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.

Previous Showing 11-19 of 19 results.

A077802 Sum of products of parts increased by 1 in hook partitions of n, where hook partitions are of the form h*1^(n-h).

Original entry on oeis.org

1, 2, 7, 18, 41, 88, 183, 374, 757, 1524, 3059, 6130, 12273, 24560, 49135, 98286, 196589, 393196, 786411, 1572842, 3145705, 6291432, 12582887, 25165798, 50331621, 100663268, 201326563, 402653154, 805306337, 1610612704
Offset: 0

Views

Author

Alford Arnold, Dec 02 2002

Keywords

Comments

It is not clear whether a(0) should be 1 or 0; this depends on whether the empty partition is a hook partition. By strict interpretation of the definition above, it is not; and except for n=0, there are exactly n hook partitions for each n. On the other hand, if defined as "a partition in whose Ferrers diagram every point is on the first row or column", the empty partition is a hook partition. - Franklin T. Adams-Watters, Jul 11 2009

Examples

			The hook partitions of 4 are 4, 3+1, 2+1+1, 1+1+1+1; the corresponding products when parts are increased by 1 are 5, 8, 12, 16; and their sum is a(4) = 41.
		

Crossrefs

Cf. A074141, A055010 (first differences), A042950 (second differences).
Cf. A132048.
Same as A095151 except for a(0). - Franklin T. Adams-Watters, Jul 11 2009

Programs

Formula

From Vladeta Jovovic, Dec 05 2002: (Start)
a(n) = 3*2^n - n - 3, n > 0.
G.f.: x*(2-x)/(1-2*x)/(1-x)^2.
Recurrence: a(n) = 4*a(n-1) - 5*a(n-2) + 2*a(n-3). (End)
Row sums of triangle A132048. Equals binomial transform of [1, 1, 4, 2, 4, 2, 4, 2, 4, ...]. - Gary W. Adamson, Aug 08 2007
a(n) = A125128(n) + A000225(n), n >= 1. - Miquel Cerda, Aug 07 2016

Extensions

More terms from John W. Layman, Dec 05 2002

A265836 Expansion of Product_{k>=1} 1/(1 - k*(k+1)*x^k).

Original entry on oeis.org

1, 2, 10, 32, 120, 342, 1206, 3320, 10604, 29578, 88342, 239400, 702020, 1863654, 5262650, 13948824, 38427192, 100244162, 272822282, 703972024, 1883948848, 4839944150, 12779850278, 32548367784, 85335644100, 215826029018, 560407835934, 1412632075328
Offset: 0

Views

Author

Vaclav Kotesovec, Dec 16 2015

Keywords

Crossrefs

Programs

  • Maple
    b:= proc(n, i) option remember; `if`(n=0 or i=1,
          2^n, b(n, i-1)+(1+i)*i*b(n-i, min(n-i, i)))
        end:
    a:= n-> b(n$2):
    seq(a(n), n=0..33);  # Alois P. Heinz, Aug 16 2019
  • Mathematica
    nmax = 40; CoefficientList[Series[Product[1/(1 - k*(k+1)*x^k), {k, 1, nmax}], {x, 0, nmax}], x]

Formula

a(n) ~ c * 6^(n/2), where
c = 79.0418032646837469192452349...... if n is even,
c = 78.4480460169710091436913691...... if n is odd.

A267008 Expansion of Product_{k>=1} (1 + (k+1)*x^k).

Original entry on oeis.org

1, 2, 3, 10, 13, 28, 58, 90, 146, 260, 481, 688, 1168, 1748, 2863, 4726, 6938, 10412, 16140, 23746, 35702, 55812, 79032, 116758, 168779, 247006, 350310, 513410, 744286, 1045466, 1485685, 2098780, 2935416, 4137878, 5746618, 8027612, 11343706, 15487222, 21418682
Offset: 0

Views

Author

Vaclav Kotesovec, Jan 08 2016

Keywords

Crossrefs

Programs

  • Maple
    b:= proc(n, i) option remember; `if`(i*(i+1)/2 b(n$2):
    seq(a(n), n=0..42);  # Alois P. Heinz, Aug 15 2019
  • Mathematica
    nmax = 50; CoefficientList[Series[Product[1+(k+1)*x^k, {k, 1, nmax}], {x, 0, nmax}], x]
    nmax = 50; poly = ConstantArray[0, nmax+1]; poly[[1]] = 1; poly[[2]] = 2; Do[Do[poly[[j+1]] += (k+1)*poly[[j-k+1]], {j, nmax, k, -1}];, {k, 2, nmax}]; poly

A079308 For a partition P of a positive integer, let f(P) be the product of k+1, over all parts k in P. Let a(n,r) be the sum of f(P) over all partitions P of n with smallest part r. Sequence gives table of a(n,r) for 1 <= r <= n, in the order a(1,1); a(2,1), a(2,2); a(3,1), a(3,2), a(3,3); ...

Original entry on oeis.org

2, 4, 3, 14, 0, 4, 36, 9, 0, 5, 100, 12, 0, 0, 6, 236, 42, 16, 0, 0, 7, 602, 54, 20, 0, 0, 0, 8, 1368, 195, 24, 25, 0, 0, 0, 9, 3242, 246, 92, 30, 0, 0, 0, 0, 10, 7240, 759, 112, 35, 36, 0, 0, 0, 0, 11, 16386, 1134, 232, 40, 42, 0, 0, 0, 0, 0, 12, 35692, 2859, 528, 170, 48, 49, 0, 0, 0, 0, 0, 13
Offset: 1

Views

Author

Alford Arnold, Feb 09 2003

Keywords

Examples

			The partitions with minimal part 3 begin 3, 3+3, 4+3, 5+3, 6+3, 3+3+3, ... which yield the following values of f: 4, 16, 20, 24, 28, 64, ... therefore the 3rd column of our table begins 4,0,0,16,20,24,(28+64)=92,...
Triangle a(n,r) begins:
:    2;
:    4,   3;
:   14,   0,   4;
:   36,   9,   0,  5;
:  100,  12,   0,  0,  6;
:  236,  42,  16,  0,  0, 7;
:  602,  54,  20,  0,  0, 0, 8;
: 1368, 195,  24, 25,  0, 0, 0, 9;
: 3242, 246,  92, 30,  0, 0, 0, 0, 10;
: 7240, 759, 112, 35, 36, 0, 0, 0,  0, 11;
		

Crossrefs

Cf. A074139, A074141 (row sums).

Programs

  • Maple
    b:= proc(n, k) option remember; `if`(n=0, 1,
          `if`(k>n, 0, b(n, k+1) +(k+1)*b(n-k, k)))
        end:
    a:= (n, k)-> b(n,k)-b(n, k+1):
    seq(seq(a(n, k), k=1..n), n=1..12);  # Alois P. Heinz, May 22 2015
  • Mathematica
    a[n_, r_] := Which[r>n, 0, r==n, n+1, True, a[n, r]=(r+1)Sum[a[n-r, s], {s, r, n-r}]]; Flatten[Table[a[n, r], {n, 1, 12}, {r, 1, n}]]

Extensions

Edited by Dean Hickerson, Feb 11 2003
Offset changed to 1 by Alois P. Heinz, May 22 2015

A078436 Triangle read by rows in which n-th row counts multisets associated with hook partitions.

Original entry on oeis.org

1, 2, 0, 3, 4, 0, 4, 6, 8, 0, 5, 8, 12, 16, 0, 6, 10, 16, 24, 32, 0, 7, 12, 20, 32, 48, 64, 0, 8, 14, 24, 40, 64, 96, 128, 0, 9, 16, 28, 48, 80, 128, 192, 256, 0, 10, 18, 32, 56, 96, 160, 256, 384, 512, 0, 11, 20, 36, 64, 112, 192, 320, 512, 768, 1024, 0, 12, 22, 40, 72, 128
Offset: 1

Views

Author

Alford Arnold, Dec 30 2002

Keywords

Comments

Row sums appear to be A077802. When more general partition types are included, such as 22^(n-4) yielding 9 18 36 72 ..., the array row sums becomes 1,2,7,18,50,118,301,... in agreement with A074141.

Examples

			Triangle begins 1; 2,0; 3,4,0; 4,6,8,0; 5,8,12,16,0; ...
a(13) = 12 because we find 1 + 3 + 4 + 3 + 1 multisets of type 21^(n-2): they are 4; 14,24,34; 114,124,134,234; 1124,1134,1234; and 11234
		

Crossrefs

Formula

G.f.: x*y*(2-x)/(1-2*x*y)/(1-x)^2. - Vladeta Jovovic, Dec 31 2002

Extensions

More terms from Vladeta Jovovic, Dec 31 2002

A079274 Number of divisors associated with the cyclic cases within the n-th group of least prime signatures.

Original entry on oeis.org

1, 0, 3, 4, 14, 18, 65, 82, 253, 378, 953, 1460, 3667, 5480, 12917, 20582, 45130, 71970, 156510, 248020, 524446, 846962, 1733252, 2806484, 5702101, 9186010, 18375867, 29872508, 58760991, 95500008, 186871472, 302966474, 587603027, 956192230
Offset: 0

Views

Author

Alford Arnold, Feb 06 2003

Keywords

Examples

			The number of divisors doubles each time we create a new "matching" partition by appending "1" to a given partition. Therefore we may write
..1..0..3..4..14..18..65..82..253..378..953...
+ ...2..4.14..36.100.236.602.1368.3242.7240...
= 1..2..7.18..50.118.301.684.1621.3620.8193...
		

Crossrefs

Cf. A074141.

Formula

a(n) = A074141(n) - 2* A074141(n-1) for n > 0 and a(0) = 1

Extensions

More terms from Pab Ter (pabrlos(AT)yahoo.com), May 27 2004

A319110 Expansion of Product_{k>=1} 1/(1 - (k - 1)*x^k).

Original entry on oeis.org

1, 0, 1, 2, 4, 6, 13, 18, 37, 56, 101, 152, 285, 410, 713, 1118, 1830, 2780, 4618, 6934, 11278, 17092, 26894, 40822, 64435, 96372, 149299, 225104, 345131, 515394, 788176, 1169962, 1772957, 2632458, 3950365, 5849260, 8748993, 12867848, 19135894, 28126614, 41598695
Offset: 0

Views

Author

Ilya Gutkovskiy, Sep 10 2018

Keywords

Crossrefs

Programs

  • Maple
    b:= proc(n, i) option remember; `if`(n=0 or i=1,
           0^n, b(n, i-1)+(i-1)*b(n-i, min(n-i, i)))
        end:
    a:= n-> b(n$2):
    seq(a(n), n=0..42);  # Alois P. Heinz, Aug 19 2019
  • Mathematica
    nmax = 40; CoefficientList[Series[Product[1/(1 - (k - 1) x^k), {k, 1, nmax}], {x, 0, nmax}], x]
    nmax = 40; CoefficientList[Series[Exp[Sum[Sum[(j - 1)^k x^(j k)/k, {j, 1, nmax}], {k, 1, nmax}]], {x, 0, nmax}], x]
    a[n_] := a[n] = If[n == 0, 1, Sum[Sum[d (d - 1)^(k/d), {d, Divisors[k]}] a[n - k], {k, 1, n}]/n]; Table[a[n], {n, 0, 40}]

Formula

G.f.: exp(Sum_{k>=1} Sum_{j>=1} (j - 1)^k*x^(j*k)/k).
From Vaclav Kotesovec, Sep 11 2018: (Start)
a(n) ~ c * 2^(2*n/5), where
c = 28108804.248904780960402246466460350520790117596512766842168... if mod(n,5) = 0
c = 28108804.010850549080284030388905319123062152339902207992657... if mod(n,5) = 1
c = 28108804.067769166625741650205643600577757560110636366636106... if mod(n,5) = 2
c = 28108804.083581827971851596540314974909801290757084687583764... if mod(n,5) = 3
c = 28108804.058853893104368046896759214442695016905368229405793... if mod(n,5) = 4
(End)

A368090 Triangle read by rows. T(n, k) = Sum_{p in P(n, k)} Product_{r in p}(r + 1), where P(n, k) are the partitions of n with length k.

Original entry on oeis.org

1, 0, 2, 0, 3, 4, 0, 4, 6, 8, 0, 5, 17, 12, 16, 0, 6, 22, 34, 24, 32, 0, 7, 43, 71, 68, 48, 64, 0, 8, 52, 122, 142, 136, 96, 128, 0, 9, 86, 197, 325, 284, 272, 192, 256, 0, 10, 100, 350, 502, 650, 568, 544, 384, 512
Offset: 0

Views

Author

Peter Luschny, Dec 11 2023

Keywords

Examples

			Triangle T(n, k) starts:
  [0] [1]
  [1] [0,  2]
  [2] [0,  3,   4]
  [3] [0,  4,   6,   8]
  [4] [0,  5,  17,  12,  16]
  [5] [0,  6,  22,  34,  24,  32]
  [6] [0,  7,  43,  71,  68,  48,  64]
  [7] [0,  8,  52, 122, 142, 136,  96, 128]
  [8] [0,  9,  86, 197, 325, 284, 272, 192, 256]
  [9] [0, 10, 100, 350, 502, 650, 568, 544, 384, 512]
		

Crossrefs

Cf. A238963, A368091, A074141 (row sums).

Programs

  • SageMath
    def T(n, k):
        return sum(product(r+1 for r in p) for p in Partitions(n, length=k))
    for n in range(10): print([T(n, k) for k in range(n + 1)])

A368091 Triangle read by rows. T(n, k) = Sum_{p in P(n, k)} Product_{r in p} r, where P(n, k) are the partitions of n with length k.

Original entry on oeis.org

1, 0, 1, 0, 2, 1, 0, 3, 2, 1, 0, 4, 7, 2, 1, 0, 5, 10, 7, 2, 1, 0, 6, 22, 18, 7, 2, 1, 0, 7, 28, 34, 18, 7, 2, 1, 0, 8, 50, 62, 50, 18, 7, 2, 1, 0, 9, 60, 121, 86, 50, 18, 7, 2, 1, 0, 10, 95, 182, 189, 118, 50, 18, 7, 2, 1
Offset: 0

Views

Author

Peter Luschny, Dec 11 2023

Keywords

Examples

			Table T(n, k) starts:
  [0] [1]
  [1] [0, 1]
  [2] [0, 2,  1]
  [3] [0, 3,  2,   1]
  [4] [0, 4,  7,   2,  1]
  [5] [0, 5, 10,   7,  2,  1]
  [6] [0, 6, 22,  18,  7,  2,  1]
  [7] [0, 7, 28,  34, 18,  7,  2, 1]
  [8] [0, 8, 50,  62, 50, 18,  7, 2, 1]
  [9] [0, 9, 60, 121, 86, 50, 18, 7, 2, 1]
		

Crossrefs

Cf. A368090, A074141, A023855, A006906 (row sums).

Programs

  • SageMath
    def T(n, k):
        return sum(product(r for r in p) for p in Partitions(n, length=k))
    for n in range(10): print([T(n, k) for k in range(n + 1)])
Previous Showing 11-19 of 19 results.