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 11-15 of 15 results.

A014809 Expansion of Jacobi theta constant (theta_2/2)^24.

Original entry on oeis.org

1, 24, 276, 2048, 11178, 48576, 177400, 565248, 1612875, 4200352, 10131156, 22892544, 48897678, 99448320, 193740408, 363315200, 658523925, 1157743824, 1980143600, 3303168000, 5386270686, 8602175744, 13477895856, 20748607488, 31425764410, 46883528256, 68969957700
Offset: 0

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Author

Keywords

Comments

Number of ways of writing n as the sum of 24 triangular numbers from A000217.

Crossrefs

Column k=24 of A286180.
Number of ways of writing n as a sum of k triangular numbers, for k=1,...: A010054, A008441, A008443, A008438, A008439, A008440, A226252, A007331, A226253, A226254, A226255, A014787, A014809.

Programs

  • Mathematica
    a[n_] := Module[{e = IntegerExponent[n+3, 2]}, (2^(11*e) * DivisorSigma[11, (n+3)/2^e] - RamanujanTau[n+3] - 2072 * If[OddQ[n], RamanujanTau[(n+3)/2], 0]) / 176896]; Array[a, 27, 0] (* Amiram Eldar, Jan 11 2025 *)

Formula

From Wolfdieter Lang, Jan 13 2017: (Start)
G.f.: 24th power of the g.f. for A010054.
a(n) = (A096963(n+3) - tau(n+3) - 2072*tau((n+3)/2))/176896, with Ramanujan's tau function given in A000594, and tau(n) is put to 0 if n is not integer. See the Ono et al. link, case k=24, Theorem 8. (End)
a(n) = 1/72 * Sum_{a, b, x, y > 0, a*x + b*y = n + 3, x == y == 1 mod 2 and a > b} (a*b)^3*(a^2 - b^2)^2. - Seiichi Manyama, May 05 2017
a(0) = 1, a(n) = (24/n)*Sum_{k=1..n} A002129(k)*a(n-k) for n > 0. - Seiichi Manyama, May 06 2017
G.f.: exp(Sum_{k>=1} 24*(x^k/k)/(1 + x^k)). - Ilya Gutkovskiy, Jul 31 2017

Extensions

More terms from Seiichi Manyama, May 05 2017

A226255 Number of ways of writing n as the sum of 11 triangular numbers.

Original entry on oeis.org

1, 11, 55, 176, 440, 957, 1848, 3245, 5412, 8580, 12892, 18888, 26895, 36916, 50160, 66935, 86658, 111870, 142582, 177320, 221100, 272690, 329065, 399102, 480040, 566808, 672969, 793760, 920326, 1074040, 1248412, 1425974, 1640595, 1882145, 2123385, 2418339, 2743928, 3062895, 3453978, 3880855
Offset: 0

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Author

N. J. A. Sloane, Jun 01 2013

Keywords

Crossrefs

Number of ways of writing n as a sum of k triangular numbers, for k=1,...: A010054, A008441, A008443, A008438, A008439, A008440, A226252, A007331, A226253, A226254, A226255, A014787, A014809.

Formula

G.f. is 11th power of g.f. for A010054.
a(0) = 1, a(n) = (11/n)*Sum_{k=1..n} A002129(k)*a(n-k) for n > 0. - Seiichi Manyama, May 06 2017
G.f.: exp(Sum_{k>=1} 11*(x^k/k)/(1 + x^k)). - Ilya Gutkovskiy, Jul 31 2017

A286180 Square array A(n,k), n>=0, k>=0, read by antidiagonals, where column k is the expansion of (Product_{j>0} (1 + x^j) * (1 - x^(2*j)))^k in powers of x.

Original entry on oeis.org

1, 1, 0, 1, 1, 0, 1, 2, 0, 0, 1, 3, 1, 1, 0, 1, 4, 3, 2, 0, 0, 1, 5, 6, 4, 2, 0, 0, 1, 6, 10, 8, 6, 0, 1, 0, 1, 7, 15, 15, 13, 3, 3, 0, 0, 1, 8, 21, 26, 25, 12, 6, 2, 0, 0, 1, 9, 28, 42, 45, 31, 14, 9, 0, 0, 0, 1, 10, 36, 64, 77, 66, 35, 24, 3, 2, 1, 0, 1, 11, 45
Offset: 0

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Author

Seiichi Manyama, May 07 2017

Keywords

Comments

A(n, k) is the number of ways of writing n as the sum of k triangular numbers.

Examples

			Square array begins:
   1, 1, 1, 1,  1,  1, ...
   0, 1, 2, 3,  4,  5, ...
   0, 0, 1, 3,  6, 10, ...
   0, 1, 2, 4,  8, 15, ...
   0, 0, 2, 6, 13, 25, ...
		

Crossrefs

Main diagonal gives A106337.

Programs

  • Mathematica
    Table[Function[k, SeriesCoefficient[Product[(1 + x^i) (1 - x^(2 i)), {i, Infinity}]^k, {x, 0, n}]][j - n], {j, 0, 12}, {n, 0, j}] // Flatten (* Michael De Vlieger, May 07 2017 *)

Formula

G.f. of column k: (Product_{j>0} (1 + x^j) * (1 - x^(2*j)))^k.

A340954 Number of ways to write n as an ordered sum of 9 nonzero triangular numbers.

Original entry on oeis.org

1, 0, 9, 0, 36, 9, 84, 72, 126, 261, 162, 576, 336, 882, 873, 1092, 1845, 1386, 3061, 2160, 4167, 3957, 4860, 6948, 5580, 10287, 7812, 12777, 12276, 14634, 18363, 17136, 25056, 21282, 31266, 28899, 36075, 39654, 41202, 51348, 49383, 63270, 59391, 76059, 73611, 87319, 93582, 96966
Offset: 9

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Author

Ilya Gutkovskiy, Jan 31 2021

Keywords

Crossrefs

Programs

  • Maple
    b:= proc(n, k) option remember; local r, t, d; r, t, d:= $0..2;
          if n=0 then `if`(k=0, 1, 0) elif k<1 then 0 else
          while t<=n do r:= r+b(n-t, k-1); t, d:= t+d, d+1 od; r fi
        end:
    a:= n-> b(n, 9):
    seq(a(n), n=9..56);  # Alois P. Heinz, Jan 31 2021
  • Mathematica
    nmax = 56; CoefficientList[Series[(EllipticTheta[2, 0, Sqrt[x]]/(2 x^(1/8)) - 1)^9, {x, 0, nmax}], x] // Drop[#, 9] &

Formula

G.f.: (theta_2(sqrt(x)) / (2 * x^(1/8)) - 1)^9, where theta_2() is the Jacobi theta function.

A341026 Number of partitions of n into 9 distinct nonzero triangular numbers.

Original entry on oeis.org

1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 1, 1, 0, 0, 0, 1, 0, 2, 0, 1, 0, 0, 2, 1, 0, 1, 1, 1, 1, 2, 0, 1, 2, 1, 2, 0, 0, 3, 1, 0, 4, 1, 2, 1, 1, 1, 2, 3, 1, 2, 3, 0, 4, 3, 2, 3, 2, 2, 1, 4, 1, 6, 3, 1, 5, 2, 2, 7, 4, 2, 3, 4, 5, 5, 5, 4, 4, 6
Offset: 165

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Author

Ilya Gutkovskiy, Feb 02 2021

Keywords

Crossrefs

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