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 1-10 of 10 results.

A298330 Number of ordered ways of writing n^2 as a sum of n squares of positive integers.

Original entry on oeis.org

1, 1, 0, 3, 1, 5, 141, 742, 6120, 43888, 300232, 3074478, 28901797, 290411147, 3175037698, 34951274416, 399750066121, 4814421349467, 59532792202344, 768079420764884, 10247011240209066, 140144002390928732, 1978092111496441512, 28633995987157024399
Offset: 0

Views

Author

Ilya Gutkovskiy, Jan 17 2018

Keywords

Examples

			a(3) = 3 because we have [4, 4, 1], [4, 1, 4] and [1, 4, 4].
		

Crossrefs

Programs

  • Maple
    G:= (JacobiTheta3(0,x)-1)/2:
    f:= proc(n) local S; S:= series(G^n,x,n^2+1); coeff(S,x,n^2) end proc:
    map(f, [$0..25]); # Robert Israel, Dec 16 2024
  • Mathematica
    Table[SeriesCoefficient[(-1 + EllipticTheta[3, 0, x])^n/2^n, {x, 0, n^2}], {n, 0, 23}]

Formula

a(n) = [x^(n^2)] (Sum_{k>=1} x^(k^2))^n.

A045847 Matrix whose (i,j)-th entry is number of representations of j as a sum of i squares of nonnegative integers; read by diagonals.

Original entry on oeis.org

1, 1, 0, 1, 1, 0, 1, 2, 0, 0, 1, 3, 1, 0, 0, 1, 4, 3, 0, 1, 0, 1, 5, 6, 1, 2, 0, 0, 1, 6, 10, 4, 3, 2, 0, 0, 1, 7, 15, 10, 5, 6, 0, 0, 0, 1, 8, 21, 20, 10, 12, 3, 0, 0, 0, 1, 9, 28, 35, 21, 21, 12, 0, 1, 1, 0, 1, 10, 36, 56, 42, 36, 30, 4, 3, 2, 0, 0, 1, 11, 45, 84, 78, 63, 61, 20, 6, 6, 2, 0, 0
Offset: 0

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Author

Keywords

Examples

			Rows are
1,0,0,..;
1,1,0,0,1,0..;
1,2,1,0,2,2,..;
1,3,3,1,...
		

Crossrefs

Diagonal gives A287617.
Antidiagonal sums give A302018.

Formula

i-th row is expansion of (1+x+x^4+x^9+...)^i.

Extensions

More terms from Erich Friedman

A298329 Number of ordered ways of writing n^2 as a sum of n squares of nonnegative integers.

Original entry on oeis.org

1, 1, 2, 6, 5, 90, 582, 4081, 45678, 378049, 3844532, 39039539, 395170118, 4589810849, 53154371025, 660113986997, 8584476248237, 113555197832758, 1572878837435750, 22259911738401660, 324143769099772448, 4869443438412466557, 74837370448784241452, 1182177603062005007658
Offset: 0

Views

Author

Ilya Gutkovskiy, Jan 17 2018

Keywords

Examples

			a(3) = 6 because we have [9, 0, 0], [4, 4, 1], [4, 1, 4], [1, 4, 4], [0, 9, 0] and [0, 0, 9].
		

Crossrefs

[x^(n^b)] (Sum_{k>=0} x^(k^b))^n: A088218 (b=1), this sequence (b=2), A298671 (b=3).

Programs

  • Maple
    b:= proc(n, i, t) option remember; `if`(n=0, 1/t!, (s->
         `if`(s*t n!*b(n^2, n$2):
    seq(a(n), n=0..25);  # Alois P. Heinz, Oct 28 2018
  • Mathematica
    Table[SeriesCoefficient[(1 + EllipticTheta[3, 0, x])^n/2^n, {x, 0, n^2}], {n, 0, 23}]
  • PARI
    {a(n) = polcoeff((sum(k=0, n, x^(k^2)+x*O(x^(n^2))))^n, n^2)} \\ Seiichi Manyama, Oct 28 2018

Formula

a(n) = [x^(n^2)] (Sum_{k>=0} x^(k^2))^n.

A291700 Number of ways of writing n as a sum of n nonnegative cubes.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 9, 73, 361, 1321, 3961, 10297, 24025, 51481, 103081, 196521, 368425, 720937, 1589161, 4069801, 11511721, 33341353, 94142313, 253860201, 650564201, 1588228228, 3716917597, 8418378043, 18699454621, 41451042556, 93508305513, 218218347865, 530189399785
Offset: 0

Views

Author

Ilya Gutkovskiy, Aug 30 2017

Keywords

Crossrefs

Main diagonal of A290054.

Programs

  • Mathematica
    Table[SeriesCoefficient[Sum[x^k^3, {k, 0, n}]^n, {x, 0, n}], {n, 0, 34}]

Formula

a(n) = [x^n] (Sum_{k>=0} x^(k^3))^n.

A302862 a(n) = [x^n] (1 + theta_3(x))^n/(2^n*(1 - x)), where theta_3() is the Jacobi theta function.

Original entry on oeis.org

1, 2, 4, 8, 20, 57, 160, 422, 1076, 2780, 7449, 20462, 56348, 153909, 418268, 1139703, 3126068, 8618611, 23801146, 65708424, 181391905, 501296216, 1387834518, 3848187985, 10680579812, 29660831057, 82415406493, 229156296047, 637659848888, 1775648562970, 4947475298595
Offset: 0

Views

Author

Ilya Gutkovskiy, Apr 14 2018

Keywords

Comments

a(n) = number of nonnegative solutions to (x_1)^2 + (x_2)^2 + ... + (x_n)^2 <= n.

Crossrefs

Programs

  • Mathematica
    Table[SeriesCoefficient[(1 + EllipticTheta[3, 0, x])^n/(2^n (1 - x)), {x, 0, n}], {n, 0, 30}]
    Table[SeriesCoefficient[1/(1 - x) Sum[x^k^2, {k, 0, n}]^n, {x, 0, n}], {n, 0, 30}]

A298938 Number of ordered ways of writing n^3 as a sum of n squares of nonnegative integers.

Original entry on oeis.org

1, 1, 1, 4, 5, 686, 13942, 455988, 13617853, 454222894, 18323165948, 802161109047, 42149084452070, 2481730049781672, 157265294178424356, 10977302934685469078, 812821237985857557677, 64539935903231450294134, 5504599828399250884049308
Offset: 0

Views

Author

Ilya Gutkovskiy, Jan 29 2018

Keywords

Examples

			a(4) = 5 because we have [64, 0, 0, 0], [16, 16, 16, 16], [0, 64, 0, 0], [0, 0, 64, 0] and [0, 0, 0, 64].
		

Crossrefs

Programs

  • Mathematica
    Table[SeriesCoefficient[(1 + EllipticTheta[3, 0, x])^n/2^n, {x, 0, n^3}], {n, 0, 18}]

Formula

a(n) = [x^(n^3)] (Sum_{k>=0} x^(k^2))^n.

A298939 Number of ordered ways of writing n^3 as a sum of n squares of positive integers.

Original entry on oeis.org

1, 1, 1, 4, 1, 286, 7582, 202028, 6473625, 226029577, 8338249868, 391526193477, 19990594900630, 1159906506684446, 74890158861242740, 5119732406649036418, 380146984328280974281, 30198665638519565614034, 2555354508318427693497565
Offset: 0

Views

Author

Ilya Gutkovskiy, Jan 29 2018

Keywords

Examples

			a(3) = 4 because we have [25, 1, 1], [9, 9, 9], [1, 25, 1] and [1, 1, 25].
		

Crossrefs

Programs

  • Mathematica
    Table[SeriesCoefficient[(-1 + EllipticTheta[3, 0, x])^n/2^n, {x, 0, n^3}], {n, 0, 18}]

Formula

a(n) = [x^(n^3)] (Sum_{k>=1} x^(k^2))^n.

A338464 Number of ways to write 2*n as an ordered sum of n squares of positive integers.

Original entry on oeis.org

1, 0, 0, 3, 0, 0, 15, 0, 8, 84, 0, 110, 495, 0, 1092, 3018, 120, 9520, 18870, 2907, 77520, 120270, 43890, 606188, 780023, 531300, 4620200, 5161377, 5651100, 34622172, 35045340, 55234560, 256503672, 245772464, 508930224, 1886151225, 1788167610, 4491607230
Offset: 0

Views

Author

Ilya Gutkovskiy, Jan 31 2021

Keywords

Comments

Also number of ways to write n as an ordered sum of n nonnegative numbers one less than a square.

Crossrefs

Programs

  • Maple
    b:= proc(n, t) option remember;
          `if`(n=0, `if`(t=0, 1, 0), `if`(t<1, 0, add((s->
          `if`(s>n, 0, b(n-s, t-1)))(j^2), j=1..isqrt(n))))
        end:
    a:= n-> b(2*n, n):
    seq(a(n), n=0..39);  # Alois P. Heinz, Feb 04 2021
  • Mathematica
    Table[SeriesCoefficient[((EllipticTheta[3, 0, x] - 1)/2)^n, {x, 0, 2 n}], {n, 0, 37}]

Formula

a(n) = [x^(2*n)] ((theta_3(x) - 1) / 2)^n, where theta_3() is the Jacobi theta function.
a(n) = [x^n] (Sum_{k>=0} x^(k*(k + 2)))^n.
a(n) = A337165(2n,n). - Alois P. Heinz, Feb 04 2021

A303172 Number of ordered ways of writing n as a sum of n square pyramidal numbers.

Original entry on oeis.org

1, 1, 1, 1, 1, 6, 31, 106, 281, 631, 1306, 2806, 6931, 19306, 55070, 150816, 391161, 977501, 2426071, 6141865, 16000186, 42465571, 112950916, 297793651, 776866355, 2015237231, 5233754306, 13668689206, 35908153534, 94633042267, 249398115466, 656105299636, 1723150461561
Offset: 0

Views

Author

Ilya Gutkovskiy, Apr 19 2018

Keywords

Crossrefs

Main diagonal of A290430.

Programs

  • Mathematica
    Table[SeriesCoefficient[Sum[x^(k (k + 1) (2 k + 1)/6), {k, 0, n}]^n, {x, 0, n}], {n, 0, 32}]

Formula

a(n) = [x^n] (Sum_{k>=0} x^(k*(k+1)*(2*k+1)/6))^n.
a(n) = A290430(n,n).

A363780 a(n) = [x^n] 1/(Sum_{k>=0} x^(k^2))^n.

Original entry on oeis.org

1, -1, 3, -10, 31, -96, 294, -876, 2511, -6796, 16698, -33540, 31174, 184534, -1627812, 8912760, -41466433, 176963760, -714194382, 2766892840, -10374065814, 37815483948, -134334781732, 465432203640, -1571910265770, 5164302815179, -16438631981418
Offset: 0

Views

Author

Seiichi Manyama, Jun 21 2023

Keywords

Crossrefs

Main diagonal of A363778.
Cf. A287617.
Showing 1-10 of 10 results.