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.

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A131995 Number of partitions of n into powers of 2 or of 3.

Original entry on oeis.org

1, 1, 2, 3, 5, 6, 9, 11, 16, 20, 26, 32, 42, 50, 62, 74, 92, 108, 131, 153, 184, 213, 251, 288, 339, 387, 448, 511, 589, 666, 761, 857, 976, 1095, 1237, 1384, 1561, 1737, 1946, 2161, 2415, 2672, 2971, 3281, 3640, 4007, 4425, 4860, 5359, 5869, 6446, 7049, 7729, 8428
Offset: 0

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Author

Reinhard Zumkeller, Aug 06 2007

Keywords

Examples

			a(10) = #{9+1, 8+2, 8+1+1, 4+4+2, 4+4+1+1, 4+3+3, 4+3+2+1,
4+3+1+1+1, 4+2+2+2, 4+2+2+1+1, 4+2+1+1+1+1, 4+1+1+1+1+1+1, 3+3+3+1,
3+3+2+2, 3+3+2+1+1, 3+3+1+1+1+1, 3+2+2+2+1, 3+2+2+1+1+1,
3+2+1+1+1+1+1, 3+1+1+1+1+1+1+1, 2+2+2+2+2, 2+2+2+2+1+1, 2+2+2+1+1+1+1,
2+2+1+1+1+1+1+1, 2+1+1+1+1+1+1+1+1, 1+1+1+1+1+1+1+1+1+1} = 26.
		

Crossrefs

Programs

  • Maple
    g:=(1-x)/(product((1-x^(2^k))*(1-x^(3^k)),k=0..10)): gser:=series(g,x=0,60): seq(coeff(gser,x,n),n=1..53); # Emeric Deutsch, Aug 26 2007

Formula

G.f.: (1-x)/Product_{k>=0} (1-x^(2^k))*(1-x^(3^k)). - Emeric Deutsch, Aug 26 2007

Extensions

Prepended a(0) = 1, Joerg Arndt and David A. Corneth, Sep 06 2020

A102434 Sum_{k=1..n} {number of partitions of n into powers k^m where 0<=m

Original entry on oeis.org

1, 5, 14, 43, 136, 477, 1733, 6459, 24338, 92413, 352753, 1352127, 5200351, 20058360, 77558825, 300540275, 1166803192, 4537567749, 17672632001, 68923264531, 269128937347, 1052049482004, 4116715363946, 16123801841726
Offset: 1

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Author

Marc LeBrun, Jan 08 2005

Keywords

Comments

Equivalently, Sum_{k=2}^n (Number of partitions of n into powers of k) + Number of partitions of n into n 1's; the latter term is C(2n-1,n).

Examples

			a(2) = 5; 3 partitions for k=1: 2.1^0, 1.1^1+1.1^0, 2.1^1; and 2 for k=2: 2.2^0, 1.2^1
		

Crossrefs

Formula

a(n) = A102433(n) - n + 1 = A102431(n) + C(2n-1,n).

Extensions

Edited and verified by Franklin T. Adams-Watters, Mar 10 2006

A309677 G.f. A(x) satisfies: A(x) = A(x^3) / (1 - x)^2.

Original entry on oeis.org

1, 2, 3, 6, 9, 12, 18, 24, 30, 42, 54, 66, 87, 108, 129, 162, 195, 228, 279, 330, 381, 456, 531, 606, 711, 816, 921, 1068, 1215, 1362, 1563, 1764, 1965, 2232, 2499, 2766, 3120, 3474, 3828, 4290, 4752, 5214, 5805, 6396, 6987, 7740, 8493, 9246, 10194, 11142
Offset: 0

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Author

Ilya Gutkovskiy, Aug 12 2019

Keywords

Comments

Self-convolution of A062051.

Crossrefs

Programs

  • Maple
    b:= proc(n, i) option remember; `if`(n=0, 1, `if`(i<0, 0,
          b(n, i-1)+(p-> `if`(p>n, 0, b(n-p, i)))(3^i)))
        end:
    a:= n-> add(b(j, ilog[3](j))*b(n-j, ilog[3](n-j)), j=0..n):
    seq(a(n), n=0..52);  # Alois P. Heinz, Aug 12 2019
  • Mathematica
    nmax = 52; A[] = 1; Do[A[x] = A[x^3]/(1 - x)^2 + O[x]^(nmax + 1) // Normal, nmax + 1]; CoefficientList[A[x], x]
    nmax = 52; CoefficientList[Series[Product[1/(1 - x^(3^k))^2, {k, 0, Floor[Log[3, nmax]] + 1}], {x, 0, nmax}], x]

Formula

G.f.: Product_{k>=0} 1/(1 - x^(3^k))^2.

A131996 Number of partitions of n into distinct powers of 2 or of 3.

Original entry on oeis.org

1, 1, 2, 2, 2, 2, 2, 2, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 6, 6, 6, 6, 6, 6, 7, 7, 7, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 9, 9, 9, 10, 10, 10, 10, 10, 10, 11, 11, 11, 12, 12, 12, 12, 12, 12
Offset: 1

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Author

Reinhard Zumkeller, Aug 06 2007

Keywords

Comments

a(A081601(n+1)) = n+1 and a(m) < n+1 for m < A081601(n+1).

Examples

			a(10) = #{9+1,8+2,4+3+2+1}=3;
a(20) = #{16+4,16+3+1,9+8+3,9+8+2+1}=4;
a(30) = #{27+3,27+2+1,16+9+4+1,16+9+3+2,16+8+4+2,16+8+3+2+1}=6.
		

Crossrefs

Programs

  • Maple
    g:=(product((1+x^(2^k))*(1+x^(3^k)),k=0..10))/(1+x): gser:=series(g,x=0,111): seq(coeff(gser,x,n),n=1..108); # Emeric Deutsch, Aug 26 2007
  • Mathematica
    max = 100; Product[((1 + x^(2^k)) (1 + x^(3^k))), {k, 0, Log[2, max] // Ceiling}]/(1 + x) + O[x]^max // CoefficientList[#, x]& // Rest (* Jean-François Alcover, Sep 30 2016 *)

Formula

G.f.: Product_{k>=0} ((1+x^(2^k))(1+x^(3^k)))/(1+x) (offset 0). - Emeric Deutsch, Aug 26 2007

A294298 Sum of products of terms in all partitions of 3*n into powers of 3.

Original entry on oeis.org

1, 4, 13, 49, 157, 481, 1534, 4693, 14170, 43357, 130918, 393601, 1188454, 3573013, 10726690, 32248957, 96815758, 290516161, 872169223, 2617128409, 7852005967, 23561605318, 70690403371, 212076797530, 636280680100, 1908892327810, 5726727270940, 17180634420931
Offset: 0

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Author

Seiichi Manyama, Oct 27 2017

Keywords

Examples

			n | partitions of 3*n into powers of 3                          | a(n)
----------------------------------------------------------------------------------
1 | 3  , 1+1+1                                                  | 3+1        =  4.
2 | 3+3, 3+1+1+1, 1+1+1+1+1+1                                   | 9+3+1      = 13.
3 | 9  , 3+3+3  , 3+3+1+1+1  , 3+1+1+1+1+1+1, 1+1+1+1+1+1+1+1+1 | 9+27+9+3+1 = 49.
		

Crossrefs

Programs

  • Maple
    b:= proc(n, i, p) option remember; `if`(n=0, p,
         `if`(i<1, 0, add(b(n-j*i, i/3, p*i^j), j=0..n/i)))
        end:
    a:= n-> (t-> b(t, 3^ilog[3](t), 1))(3*n):
    seq(a(n), n=0..33);  # Alois P. Heinz, Oct 27 2017
  • Mathematica
    b[n_, i_, p_] := b[n, i, p] = If[n == 0, p, If[i < 1, 0, Sum[b[n - j i, i/3, p i^j], {j, 0, n/i}]]];
    a[n_] := b[3n, 3^Floor@Log[3, 3n], 1];
    a /@ Range[0, 33] (* Jean-François Alcover, Nov 23 2020, after Alois P. Heinz *)

Formula

a(n) = [x^(3*n)] Product_{k>=0} 1/(1 - 3^k*x^(3^k)). - Ilya Gutkovskiy, Sep 10 2018
a(n) ~ c * 3^n, where c = 2.2530906593645919365992433370928351696108819534655299832797806149219665... - Vaclav Kotesovec, Jun 18 2019

A355915 Number of ways to write n as a sum of numbers of the form 2^r * 3^s, where r and s are >= 0, and no summand divides another.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 2, 1, 1, 1, 1, 1, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 2, 1, 1, 2, 1, 1, 2, 1, 1, 2, 1, 3, 1, 1, 1, 2, 1, 1, 1, 2, 2, 1, 1, 1, 2, 1, 1, 3, 2, 2, 1, 1, 2, 2, 1, 2, 2, 1, 2, 1, 1, 2, 1, 1, 2, 2, 1, 3, 1, 2, 2, 3, 1, 2, 1, 2, 2, 2, 1, 3, 3, 2, 1
Offset: 1

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Author

Keywords

Comments

It is a theorem of Erdos [Erdős] that this representation is always possible.
Without the divisibility constraint the answer is A062051.
See A356792 for when k first appears.

Examples

			Illustration of initial terms:
1 = 2^0
2 = 2^1
3 = 3^1
4 = 2^2
5 = 2+3
6 = 2*3
7 = 2^2+3
8 = 2^3
9 = 3^2
10 = 2^2 + 2*3
11 = 2+3^2 = 2^3+3 (this is the first time there are 2 solutions)
12 = 2^2*3
13 = 2^2+3^2
14 = 2^3+2*3
...
		

Crossrefs

Programs

  • Python
    # see linked program

Extensions

More than the usual number of terms are shown, to distinguish this from similar sequences.

A112582 Number of partitions of n into distinct 5-smooth parts.

Original entry on oeis.org

1, 1, 2, 2, 3, 4, 4, 5, 7, 8, 9, 11, 12, 14, 18, 19, 21, 26, 28, 32, 37, 39, 44, 51, 56, 61, 70, 76, 83, 96, 102, 111, 126, 135, 148, 165, 176, 191, 212, 228, 245, 270, 289, 310, 344, 365, 390, 428, 454, 489, 531, 563, 602, 654, 697, 740, 800, 848, 902, 977, 1031, 1093
Offset: 1

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Author

Reinhard Zumkeller, Sep 14 2005

Keywords

Crossrefs

A272344 Positive integers n where the number of parts function on the set of 3-ary partitions of n is equidistributed mod 3.

Original entry on oeis.org

6, 7, 8, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 33, 34, 35, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 87, 88, 89, 96, 97, 98, 99, 100, 101
Offset: 1

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Author

Tom Edgar, Apr 26 2016

Keywords

Comments

An integer n is in the list if and only if n_i=2 for some index i>0 where n = Sum_{i>=0}n_i3^i is the base 3 representation of n.
Appears to be the complement of A096304.

Examples

			There are three 3-ary partitions of 6: one has 2 parts (3+3), one has 4 parts (3+1+1+1), and one has 6 parts (1+1+1+1+1+1); thus, modulo 3, the number of parts function is equidistributed mod 3 and so 6 is a term.
There are five 3-ary partitions of 9 so the number of parts function cannot be equidistributed mod 3. Thus, 9 is not a term.
		

Crossrefs

Programs

  • Sage
    M=[n for n in [1..105] if (2) in n.digits(3)[1:]]

A308558 Triangle read by rows where T(n,k) is the number of integer partitions of n > 0 into powers of k > 0.

Original entry on oeis.org

1, 1, 2, 1, 2, 2, 1, 4, 2, 2, 1, 4, 2, 2, 2, 1, 6, 3, 2, 2, 2, 1, 6, 3, 2, 2, 2, 2, 1, 10, 3, 3, 2, 2, 2, 2, 1, 10, 5, 3, 2, 2, 2, 2, 2, 1, 14, 5, 3, 3, 2, 2, 2, 2, 2, 1, 14, 5, 3, 3, 2, 2, 2, 2, 2, 2, 1, 20, 7, 4, 3, 3, 2, 2, 2, 2, 2, 2, 1, 20, 7, 4, 3, 3, 2
Offset: 1

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Author

Gus Wiseman, Jun 07 2019

Keywords

Examples

			Triangle begins:
  1
  1  2
  1  2  2
  1  4  2  2
  1  4  2  2  2
  1  6  3  2  2  2
  1  6  3  2  2  2  2
  1 10  3  3  2  2  2  2
  1 10  5  3  2  2  2  2  2
  1 14  5  3  3  2  2  2  2  2
  1 14  5  3  3  2  2  2  2  2  2
  1 20  7  4  3  3  2  2  2  2  2  2
  1 20  7  4  3  3  2  2  2  2  2  2  2
Row n = 6 counts the following partitions:
  (111111)  (42)      (33)      (411)     (51)      (6)
            (222)     (3111)    (111111)  (111111)  (111111)
            (411)     (111111)
            (2211)
            (21111)
            (111111)
		

Crossrefs

Same as A102430 except for the k = 1 column.
Row sums are A102431(n) + 1.
Column k = 2 is A018819.
Column k = 3 is A062051.

Programs

  • Mathematica
    Table[If[k==1,1,Length[Select[IntegerPartitions[n],And@@(IntegerQ[Log[k,#]]&/@#)&]]],{n,10},{k,n}]

A339279 Number of partitions of 3*n into powers of 3 where every part appears at least 2 times.

Original entry on oeis.org

1, 1, 2, 3, 4, 5, 7, 8, 10, 13, 15, 18, 22, 25, 29, 34, 38, 43, 50, 55, 62, 70, 77, 85, 95, 103, 113, 126, 136, 149, 164, 177, 192, 210, 225, 243, 265, 283, 305, 330, 352, 377, 406, 431, 460, 494, 523, 557, 595, 629, 667, 710, 748, 791, 841, 884, 934, 989, 1039, 1094, 1156
Offset: 0

Views

Author

Ilya Gutkovskiy, Nov 29 2020

Keywords

Examples

			a(3) = 3 because we have [3, 3, 3], [3, 3, 1, 1, 1] and [1, 1, 1, 1, 1, 1, 1, 1, 1].
		

Crossrefs

Programs

  • Mathematica
    nmax = 60; CoefficientList[Series[(1/(1 - x^2)) Product[1/(1 - x^(3^k)), {k, 0, Floor[Log[3, nmax]] + 1}], {x, 0, nmax}], x]
    A005704[0] = 1; A005704[n_] := A005704[n] = A005704[n - 1] + A005704[Floor[n/3]]; a[n_] := Sum[(-1)^(n - k) A005704[k], {k, 0, n}]; Table[a[n], {n, 0, 60}]

Formula

G.f.: (1/(1 - x^2)) * Product_{k>=0} 1/(1 - x^(3^k)).
G.f.: (1/(1 - x)) * Product_{k>=0} (1 + x^(2*3^k)/(1 - x^(3^k))).
a(n) = [x^(3*n)] Product_{k>=0} (1 + x^(2*3^k)/(1 - x^(3^k))).
a(n) = Sum_{k=0..n} (-1)^(n-k) * A005704(k).
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