cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-6 of 6 results.

A211978 Total number of parts in all partitions of n plus the sum of largest parts of all partitions of n.

Original entry on oeis.org

0, 2, 6, 12, 24, 40, 70, 108, 172, 256, 384, 550, 798, 1112, 1560, 2136, 2926, 3930, 5288, 6996, 9260, 12104, 15798, 20412, 26348, 33702, 43044, 54588, 69090, 86906, 109126, 136270, 169854, 210732, 260924, 321752, 396028, 485624, 594402, 725174, 883092, 1072208
Offset: 0

Views

Author

Omar E. Pol, Jan 03 2013

Keywords

Comments

Also twice A006128, because the total number of parts in all partitions of n equals the sum of largest parts of all partitions of n. For a proof without words see the illustration of initial terms. Note that the sum of the lengths of all horizontal segments equals the sum of largest parts of all partitions of n. On the other hand, the sum of the lengths of all vertical segments equals the total number of parts of all partition of n. Therefore the sum of lengths of all horizontal segments equals the sum of lengths of all vertical segments.
a(n) is also the sum of the semiperimeters of the Ferrers boards of the partitions of n. Example: a(2)=6; indeed, the Ferrers boards of the partitions [2] and [1,1] of 2 are 2x1 rectangles; the sum of their semiperimeters is 3 + 3 = 6. - Emeric Deutsch, Oct 07 2016
a(n) is also the sum of the semiperimeters of the regions of the set of partitions of n. See the first illustration in the Example section. For more information see A278355. - Omar E. Pol, Nov 23 2016

Examples

			Illustration of initial terms as a minimalist diagram of regions of the set of partitions of n, for n = 1..6:
.                                         _ _ _ _ _ _
.                                         _ _ _      |
.                                         _ _ _|_    |
.                                         _ _    |   |
.                             _ _ _ _ _   _ _|_ _|_  |
.                             _ _ _    |  _ _ _    | |
.                   _ _ _ _   _ _ _|_  |  _ _ _|_  | |
.                   _ _    |  _ _    | |  _ _    | | |
.           _ _ _   _ _|_  |  _ _|_  | |  _ _|_  | | |
.     _ _   _ _  |  _ _  | |  _ _  | | |  _ _  | | | |
. _   _  |  _  | |  _  | | |  _  | | | |  _  | | | | |
.  |   | |   | | |   | | | |   | | | | |   | | | | | |
.
. 2    6     12        24         40          70
.
Also using the elements from the diagram we can draw an infinite Dyck path in which the n-th odd-indexed segment has A141285(n) up-steps and the n-th even-indexed segment has A194446(n) down-steps. Note that the n-th largest peak between two valleys at height 0 is also the partition number A000041(n) as shown below:
.
11...........................................................
.                                                           /\
.                                                          /  \
.                                                         /    \
7..................................                      /      \
.                                 /\                    /        \
5....................            /  \                /\/          \
.                   /\          /    \          /\  /              \
3..........        /  \        /      \        /  \/                \
2.....    /\      /    \    /\/        \      /                      \
1..  /\  /  \  /\/      \  /            \  /\/                        \
0 /\/  \/    \/          \/              \/                            \
. 0,2,  6,   12,         24,             40,                          70...
.
		

Crossrefs

Programs

  • Maple
    Q := sum(x^j/(1-x^j), j = 1 .. i): R := product(1-x^j, j = 1 .. i): g := sum(x^i*(1+i+Q)/R, i = 1 .. 100): gser := series(g, x = 0, 50): seq(coeff(gser, x, n), n = 0 .. 41); # Emeric Deutsch, Oct 07 2016
  • Mathematica
    Array[2 Sum[DivisorSigma[0, m] PartitionsP[# - m], {m, #}] &, 42, 0] (* Michael De Vlieger, Mar 20 2020 *)

Formula

a(n) = 2*A006128(n).
a(n) = A225600(2*A000041(n)) = A225600(A139582(n)), n >= 1.
a(n) = (Sum_{m=1..p(n)} A194446(m)) + (Sum_{m=1..p(n)} A141285(m)) = 2*Sum_{m=1..p(n)} A194446(m) = 2*Sum_{m=1..p(n)} A141285(m), where p(n) = A000041(n), n >= 1.
The trivariate g.f. G(t,s,x) of the partitions of a nonnegative integer relative to weight (marked by x), number of parts (marked by t), and largest part (marked by s) is G(t,s,x) = Sum_{i>=1} t*s^i*x^i/product_{j=1..i} (1-tx^j). Setting s = t, we obtain the bivariate g.f. of the partitions relative to weight (marked by x) and semiperimeter of the Ferrers board (marked by t). The g.f. of a(n) is g(x) = Sum_{i>=1} ((x^i*(1 + i + Q(x))/R(x)), where Q(x) = sum_{j=1..i} (x^j/(1 - x^j)) and R(x) = product_{j=1..i}(1-x^j). g(x) has been obtained by setting t = 1 in dG(t,t,x))/dt. - Emeric Deutsch, Oct 07 2016

A299474 a(n) = 4*p(n), where p(n) is the number of partitions of n.

Original entry on oeis.org

4, 4, 8, 12, 20, 28, 44, 60, 88, 120, 168, 224, 308, 404, 540, 704, 924, 1188, 1540, 1960, 2508, 3168, 4008, 5020, 6300, 7832, 9744, 12040, 14872, 18260, 22416, 27368, 33396, 40572, 49240, 59532, 71908, 86548, 104060, 124740, 149352, 178332, 212696, 253044, 300700, 356536, 422232, 499016, 589092, 694100, 816904
Offset: 0

Views

Author

Omar E. Pol, Feb 10 2018

Keywords

Comments

For n >= 1, a(n) is also the number of edges in the diagram of partitions of n, in which A299475(n) is the number of vertices and A000041(n) is the number of regions (see example and Euler's formula).

Examples

			Construction of a modular table of partitions in which a(n) is the number of edges of the diagram after n-th stage (n = 1..6):
--------------------------------------------------------------------------------
n ........:   1     2       3         4           5             6     (stage)
a(n)......:   4     8      12        20          28            44     (edges)
A299475(n):   4     7      10        16          22            34     (vertices)
A000041(n):   1     2       3         5           7            11     (regions)
--------------------------------------------------------------------------------
r     p(n)
--------------------------------------------------------------------------------
.             _    _ _    _ _ _    _ _ _ _    _ _ _ _ _    _ _ _ _ _ _
1 .... 1 ....|_|  |_| |  |_| | |  |_| | | |  |_| | | | |  |_| | | | | |
2 .... 2 .........|_ _|  |_ _| |  |_ _| | |  |_ _| | | |  |_ _| | | | |
3 .... 3 ................|_ _ _|  |_ _ _| |  |_ _ _| | |  |_ _ _| | | |
4                                 |_ _|   |  |_ _|   | |  |_ _|   | | |
5 .... 5 .........................|_ _ _ _|  |_ _ _ _| |  |_ _ _ _| | |
6                                            |_ _ _|   |  |_ _ _|   | |
7 .... 7 ....................................|_ _ _ _ _|  |_ _ _ _ _| |
8                                                         |_ _|   |   |
9                                                         |_ _ _ _|   |
10                                                        |_ _ _|     |
11 .. 11 .................................................|_ _ _ _ _ _|
.
Apart from the axis x, the r-th horizontal line segment has length A141285(r), equaling the largest part of the r-th region of the diagram.
Apart from the axis y, the r-th vertical line segment has length A194446(r), equaling the number of parts in the r-th region of the diagram.
The total number of parts equals the sum of largest parts.
Note that every diagram contains all previous diagrams.
An infinite diagram is a table of all partitions of all positive integers.
		

Crossrefs

k times partition numbers: A000041 (k=1), A139582 (k=2), A299473 (k=3), this sequence (k=4).

Programs

  • GAP
    List([0..50],n->4*NrPartitions(n)); # Muniru A Asiru, Jul 10 2018
    
  • Maple
    with(combinat): seq(4*numbpart(n),n=0..50); # Muniru A Asiru, Jul 10 2018
  • Mathematica
    4*PartitionsP[Range[0,50]] (* Harvey P. Dale, Dec 05 2023 *)
  • PARI
    a(n) = 4*numbpart(n); \\ Michel Marcus, Jul 15 2018
    
  • Python
    from sympy.ntheory import npartitions
    def a(n): return 4*npartitions(n)
    print([a(n) for n in range(51)]) # Michael S. Branicky, Apr 04 2021

Formula

a(n) = 4*A000041(n) = 2*A139582(n).
a(n) = A000041(n) + A299475(n) - 1, n >= 1 (Euler's formula).
a(n) = A000041(n) + A299473(n). - Omar E. Pol, Aug 11 2018

A299475 a(n) is the number of vertices in the diagram of partitions of n (see example).

Original entry on oeis.org

1, 4, 7, 10, 16, 22, 34, 46, 67, 91, 127, 169, 232, 304, 406, 529, 694, 892, 1156, 1471, 1882, 2377, 3007, 3766, 4726, 5875, 7309, 9031, 11155, 13696, 16813, 20527, 25048, 30430, 36931, 44650, 53932, 64912, 78046, 93556, 112015, 133750, 159523, 189784, 225526, 267403, 316675, 374263, 441820, 520576, 612679
Offset: 0

Views

Author

Omar E. Pol, Feb 11 2018

Keywords

Comments

For n >= 1, A299474(n) is the number of edges and A000041(n) is the number of regions in the mentioned diagram (see example and Euler's formula).

Examples

			Construction of a modular table of partitions in which a(n) is the number of vertices of the diagram after n-th stage (n = 1..6):
--------------------------------------------------------------------------------
n ........:   1     2       3         4           5             6     (stage)
a(n)......:   4     7      10        16          22            34     (vertices)
A299474(n):   4     8      12        20          28            44     (edges)
A000041(n):   1     2       3         5           7            11     (regions)
--------------------------------------------------------------------------------
r     p(n)
--------------------------------------------------------------------------------
.             _    _ _    _ _ _    _ _ _ _    _ _ _ _ _    _ _ _ _ _ _
1 .... 1 ....|_|  |_| |  |_| | |  |_| | | |  |_| | | | |  |_| | | | | |
2 .... 2 .........|_ _|  |_ _| |  |_ _| | |  |_ _| | | |  |_ _| | | | |
3 .... 3 ................|_ _ _|  |_ _ _| |  |_ _ _| | |  |_ _ _| | | |
4                                 |_ _|   |  |_ _|   | |  |_ _|   | | |
5 .... 5 .........................|_ _ _ _|  |_ _ _ _| |  |_ _ _ _| | |
6                                            |_ _ _|   |  |_ _ _|   | |
7 .... 7 ....................................|_ _ _ _ _|  |_ _ _ _ _| |
8                                                         |_ _|   |   |
9                                                         |_ _ _ _|   |
10                                                        |_ _ _|     |
11 .. 11 .................................................|_ _ _ _ _ _|
.
Apart from the axis x, the r-th horizontal line segment has length A141285(r), equaling the largest part of the r-th region of the diagram.
Apart from the axis y, the r-th vertical line segment has length A194446(r), equaling the number of parts in the r-th region of the diagram.
The total number of parts equals the sum of largest parts.
Note that every diagram contains all previous diagrams.
An infinite diagram is a table of all partitions of all positive integers.
		

Crossrefs

Programs

  • PARI
    a(n) = if (n==0, 1, 1+3*numbpart(n)); \\ Michel Marcus, Jul 15 2018

Formula

a(0) = 1; a(n) = 1 + 3*A000041(n), n >= 1.
a(n) = A299474(n) - A000041(n) + 1, n >= 1 (Euler's formula).

A278602 Sum of the perimeters of all regions of the n-th section of a modular table of partitions.

Original entry on oeis.org

0, 4, 8, 12, 24, 32, 60, 76, 128, 168, 256, 332, 496, 628, 896, 1152, 1580, 2008, 2716, 3416, 4528, 5688, 7388, 9228, 11872, 14708, 18684, 23088, 29004, 35632, 44440, 54288, 67168, 81756, 100384, 121656, 148552, 179192, 217556, 261544, 315836, 378232, 454748, 542584, 649500, 772532, 920912
Offset: 0

Views

Author

Omar E. Pol, Nov 23 2016

Keywords

Comments

Consider an infinite dissection of the fourth quadrant of the square grid in which, apart from the axes x and y, the k-th horizontal line segment has length A141285(k) and the k-th vertical line segment has length A194446(k). Both line segments shares the point (A141285(k),k). For n>=1, the table contains A000041(n) regions which are distributed in n sections. Note that in the infinite table there are no partitions because every row contains an infinite number of parts. On the other hand, taking only the first n sections from the table we have a representation of the partitions of n. For an illustration see the example. For the definition of "region" see A206437. For the definition of "section" see A135010. For a visualization of the corner of size n X n of the table see A273140.
a(n) is also the sum of the perimeters of the Ferrers boards of the partitions of n, minus the sum of the perimeters of the Ferrers boards of the partitions of n-1, with n >= 1. For more information see A278355.

Examples

			For n = 1..6, consider the modular table of partitions for the first six positive integers as shown below in the fourth quadrant of the square grid (see Figure 1):
|--------------|-----------------------------------------------------|
| Modular table|                      Sections                       |
| of partitions|-----------------------------------------------------|
|  for n=1..6  | 1     2       3         4           5             6 |
1--------------|-----------------------------------------------------|
.  _ _ _ _ _ _   _     _       _         _           _             _
. |_| | | | | | |_|  _| |     | |       | |         | |           | |
. |_ _| | | | |     |_ _|  _ _| |       | |         | |           | |
. |_ _ _| | | |           |_ _ _|  _ _ _| |         | |           | |
. |_ _|   | | |                   |_ _|   |         | |           | |
. |_ _ _ _| | |                   |_ _ _ _|  _ _ _ _| |           | |
. |_ _ _|   | |                             |_ _ _|   |           | |
. |_ _ _ _ _| |                             |_ _ _ _ _|  _ _ _ _ _| |
. |_ _|   |   |                                         |_ _|   |   |
. |_ _ _ _|   |                                         |_ _ _ _|   |
. |_ _ _|     |                                         |_ _ _|     |
. |_ _ _ _ _ _|                                         |_ _ _ _ _ _|
.
.   Figure 1.                         Figure 2.
.
The table contains 11 regions, see Figure 1.
The regions are distributed in 6 sections. The Figure 2 shows the sections separately.
Then consider the following table which contains the diagram of every region separately:
---------------------------------------------------------------------
|         |         |         |                    |       |        |
| Section | Region  |  Parts  |       Region       | Peri- |  a(n)  |
|         |         |(A220482)|       diagram      | meter |        |
---------------------------------------------------------------------
|         |         |         |      _             |       |        |
|    1    |    1    |    1    |     |_|            |   4   |    4   |
---------------------------------------------------------------------
|         |         |         |        _           |       |        |
|         |         |    1    |      _| |          |       |        |
|    2    |    2    |    2    |     |_ _|          |   8   |    8   |
---------------------------------------------------------------------
|         |         |         |          _         |       |        |
|         |         |    1    |         | |        |       |        |
|         |         |    1    |      _ _| |        |       |        |
|    3    |    3    |    3    |     |_ _ _|        |  12   |   12   |
---------------------------------------------------------------------
|         |         |         |      _ _           |       |        |
|         |    4    |    2    |     |_ _|          |   6   |        |
|         |---------|---------|----------------------------|        |
|         |         |         |            _       |       |        |
|         |         |    1    |           | |      |       |        |
|         |         |    1    |           | |      |       |        |
|         |         |    1    |          _| |      |       |        |
|         |         |    2    |      _ _|   |      |       |        |
|    4    |    5    |    4    |     |_ _ _ _|      |  18   |   24   |
---------------------------------------------------------------------
|         |         |         |      _ _ _         |       |        |
|         |    6    |    3    |     |_ _ _|        |   8   |        |
|         |---------|---------|--------------------|-------|        |
|         |         |         |              _     |       |        |
|         |         |    1    |             | |    |       |        |
|         |         |    1    |             | |    |       |        |
|         |         |    1    |             | |    |       |        |
|         |         |    1    |             | |    |       |        |
|         |         |    1    |            _| |    |       |        |
|         |         |    2    |      _ _ _|   |    |       |        |
|    5    |    7    |    5    |     |_ _ _ _ _|    |  24   |   32   |
---------------------------------------------------------------------
|         |         |         |      _ _           |       |        |
|         |    8    |    2    |     |_ _|          |   6   |        |
|         |---------|---------|--------------------|-------|        |
|         |         |         |          _ _       |       |        |
|         |         |    2    |      _ _|   |      |       |        |
|         |    9    |    4    |     |_ _ _ _|      |  12   |        |
1         |---------|---------|--------------------|-------|        |
|         |         |         |      _ _ _         |       |        |
|         |   10    |    3    |     |_ _ _|        |   8   |        |
|         |---------|---------|--------------------|-------|        |
|         |         |         |                _   |       |        |
|         |         |    1    |               | |  |       |        |
|         |         |    1    |               | |  |       |        |
|         |         |    1    |               | |  |       |        |
|         |         |    1    |               | |  |       |        |
|         |         |    1    |               | |  |       |        |
|         |         |    1    |               | |  |       |        |
|         |         |    1    |              _| |  |       |        |
|         |         |    2    |             |   |  |       |        |
|         |         |    2    |            _|   |  |       |        |
|         |         |    3    |      _ _ _|     |  |       |        |
|    6    |   11    |    6    |     |_ _ _ _ _ _|  |  34   |   60   |
---------------------------------------------------------------------
.
For n = 1..3, there is only one region in every section. The perimeters of the regions are 4, 8 and 12 respectively, so a(1) = 4, a(2) = 8, and a(3) = 12.
For n = 4, the 4th section contains two regions with perimeters 6 and 18 respectively. The sum of the perimeters is 6 + 18 = 24, so a(4) = 24.
For n = 5, the 5th section contains two regions with perimeters 8 and 24 respectively. The sum of the perimeters is 8 + 24 = 32, so a(5) = 32.
For n = 6, the 6th section contains four regions with perimeters 6, 12, 8 and 34 respectively. The sum of the perimeters is 6 + 12 + 8 + 34 = 60, so a(6) = 60.
		

Crossrefs

Formula

a(n) = 4 * A138137(n) = 2 * A233968(n), n >= 1 in both cases.

A299473 a(n) = 3*p(n), where p(n) is the number of partitions of n.

Original entry on oeis.org

3, 3, 6, 9, 15, 21, 33, 45, 66, 90, 126, 168, 231, 303, 405, 528, 693, 891, 1155, 1470, 1881, 2376, 3006, 3765, 4725, 5874, 7308, 9030, 11154, 13695, 16812, 20526, 25047, 30429, 36930, 44649, 53931, 64911, 78045, 93555, 112014, 133749, 159522, 189783, 225525, 267402, 316674, 374262, 441819, 520575, 612678
Offset: 0

Views

Author

Omar E. Pol, Feb 10 2018

Keywords

Comments

For n >= 1, a(n) is also the number of vertices in the minimalist diagram of partitions of n, in which A139582(n) is the number of line segments and A000041(n) is the number of open regions (see example).

Examples

			Construction of a minimalist version of a modular table of partitions in which a(n) is the number of vertices of the diagram after n-th stage (n = 1..6):
-----------------------------------------------------------------------------------
n.........:    1     2       3         4           5           6   (stage)
A000041(n):    1     2       3         5           7          11   (open regions)
A139582(n):    2     4       6        10          14          22   (line segments)
a(n)......:    3     6       9        15          21          33   (vertices)
-----------------------------------------------------------------------------------
r     p(n)
-----------------------------------------------------------------------------------
.
1 .... 1 .... _|   _| |   _| | |   _| | | |   _| | | | |   _| | | | | |
2 .... 2 ......... _ _|   _ _| |   _ _| | |   _ _| | | |   _ _| | | | |
3 .... 3 ................ _ _ _|   _ _ _| |   _ _ _| | |   _ _ _| | | |
4                                  _ _|   |   _ _|   | |   _ _|   | | |
5 .... 5 ......................... _ _ _ _|   _ _ _ _| |   _ _ _ _| | |
6                                             _ _ _|   |   _ _ _|   | |
7 .... 7 .................................... _ _ _ _ _|   _ _ _ _ _| |
8                                                          _ _|   |   |
9                                                          _ _ _ _|   |
10                                                         _ _ _|     |
11 .. 11 ................................................. _ _ _ _ _ _|
.
The r-th horizontal line segment has length A141285(r).
The r-th vertical line segment has length A194446(r).
An infinite diagram is a minimalist table of all partitions of all positive integers.
		

Crossrefs

k times partition numbers: A000041 (k=1), A139582 (k=2), this sequence (k=3), A299474 (k=4).

Formula

a(n) = 3*A000041(n) = A000041(n) + A139582(n).
a(n) = A299475(n) - 1, n >= 1.

A338969 a(n) is the sum of the lengths of all the segments used to draw a rectangle of height partition(n) and width n divided into partition(n) rectangles of unit height, in turn, divided into rectangles of unit height and lengths corresponding to the parts of the partitions of n.

Original entry on oeis.org

4, 11, 21, 41, 67, 118, 181, 292, 437, 664, 958, 1412, 1983, 2819, 3899, 5406, 7328, 9977, 13317, 17817, 23497, 30967, 40349, 52573, 67784, 87320, 111601, 142395, 180432, 228317, 287110, 360476, 450261, 561346, 696699, 863199, 1065055, 1311824, 1610026, 1972444
Offset: 1

Views

Author

Stefano Spezia, Dec 23 2020

Keywords

Examples

			Illustrations for n = 1..6:
      _           _ _          _ _ _
     |_|         |_ _|        |_ _ _|
                 |_|_|        |_ _|_|
                              |_|_|_|
  a(1) = 4     a(2) = 11     a(3) = 21
   _ _ _ _     _ _ _ _ _    _ _ _ _ _ _
  |_ _ _ _|   |_ _ _ _ _|  |_ _ _ _ _ _|
  |_ _ _|_|   |_ _ _ _|_|  |_ _ _ _ _|_|
  |_ _|_ _|   |_ _ _|_ _|  |_ _ _ _|_ _|
  |_ _|_|_|   |_ _ _|_|_|  |_ _ _ _|_|_|
  |_|_|_|_|   |_ _|_ _|_|  |_ _ _|_ _ _|
              |_ _|_|_|_|  |_ _ _|_ _|_|
              |_|_|_|_|_|  |_ _ _|_|_|_|
                           |_ _|_ _|_ _|
                           |_ _|_ _|_|_|
                           |_ _|_|_|_|_|
                           |_|_|_|_|_|_|
  a(4) = 41    a(5) = 67    a(6) = 118
		

Crossrefs

Programs

  • Mathematica
    a[n_]:=(n+1)PartitionsP[n]+n+Sum[DivisorSigma[0,m] PartitionsP[n-m], {m,n}]; Table[a[n],{n,40}]

Formula

a(n) = (n + 1)*A000041(n) + n + A006128(n).
a(n) = A066186(n) + A000041(n) + A225596(n).
Showing 1-6 of 6 results.