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 1-5 of 5 results.

A363639 Expansion of Sum_{k>0} (1/(1 - k*x^k)^3 - 1).

Original entry on oeis.org

3, 12, 19, 51, 36, 180, 57, 405, 352, 918, 111, 3990, 144, 5064, 6534, 15945, 222, 51462, 267, 99354, 82478, 160812, 369, 808490, 66051, 861630, 1090342, 2593614, 552, 8966414, 621, 13039761, 13831470, 22415778, 3166218, 114011229, 852, 110103540, 167426822
Offset: 1

Views

Author

Seiichi Manyama, Jun 13 2023

Keywords

Crossrefs

Cf. A338662, A362683, A363640.
Cf. A363642, A363643, A363644.
Cf. A363628, A363647.

Programs

  • Mathematica
    a[n_] := DivisorSum[n, (n/#)^# * Binomial[# + 2, 2] &]; Array[a, 40] (* Amiram Eldar, Jul 17 2023 *)
  • PARI
    a(n) = sumdiv(n, d, (n/d)^d*binomial(d+2, 2));

Formula

a(n) = Sum_{d|n} (n/d)^d * binomial(d+2,2).

A362683 Expansion of Sum_{k>0} (1/(1 - k*x^k)^2 - 1).

Original entry on oeis.org

2, 7, 10, 25, 16, 78, 22, 153, 136, 298, 34, 1254, 40, 1214, 2004, 3825, 52, 11385, 58, 20894, 18932, 25006, 70, 150002, 18826, 115274, 199828, 389510, 88, 1334624, 94, 1725281, 2131188, 2360266, 725948, 14878299, 112, 10486958, 22329428, 37317986, 124, 120957336, 130
Offset: 1

Views

Author

Seiichi Manyama, Jun 13 2023

Keywords

Crossrefs

Cf. A338662, A363639, A363640.
Cf. A007503, A055225, A359103, A363646.

Programs

  • Mathematica
    a[n_] := DivisorSum[n, (n/#)^# * (# + 1) &]; Array[a, 50] (* Amiram Eldar, Jul 17 2023 *)
  • PARI
    a(n) = sumdiv(n, d, (n/d)^d*(d+1));

Formula

a(n) = Sum_{d|n} (n/d)^d * (d+1) = A055225(n) + A359103(n).
If p is prime, a(p) = 1 + 3*p.

A363648 Expansion of Sum_{k>0} (1/(1 - (k*x)^k)^4 - 1).

Original entry on oeis.org

4, 26, 128, 1219, 12556, 195278, 3294292, 67773349, 1550075836, 40097713880, 1141246682808, 35686524105658, 1211500426369572, 44454809534927314, 1751576172678539608, 73789791194939982793, 3308961047545347057848, 157387135278770854655312
Offset: 1

Views

Author

Seiichi Manyama, Jun 13 2023

Keywords

Crossrefs

Cf. A023887, A338663, A363646, A363647.
Cf. A363640.

Programs

  • Mathematica
    a[n_] := DivisorSum[n, (n/#)^n * Binomial[# + 3, 3] &]; Array[a, 20] (* Amiram Eldar, Jul 17 2023 *)
  • PARI
    a(n) = sumdiv(n, d, (n/d)^n*binomial(d+3, 3));

Formula

a(n) = Sum_{d|n} (n/d)^n * binomial(d+3,3).

A363661 a(n) = Sum_{d|n} (n/d)^d * binomial(d+n,n).

Original entry on oeis.org

2, 12, 32, 150, 282, 1890, 3488, 21582, 54650, 282612, 705564, 4072224, 10400782, 55006530, 158987232, 790611350, 2333606526, 11573213196, 35345264180, 168673694070, 540848064614, 2500462200182, 8233430728152, 37445946291600, 126411051769652
Offset: 1

Views

Author

Seiichi Manyama, Jun 14 2023

Keywords

Comments

All terms are even. - Robert Israel, Nov 23 2023

Links

Crossrefs

Cf. A362683, A363639, A363640.
Cf. A055225, A363660, A363662, A363663.

Programs

  • Maple
    f:= proc(n) local d;
   add((n/d)^d * binomial(n+d,n), d = numtheory:-divisors(n))
end proc:
map(f, [$1..30]); # Robert Israel, Nov 23 2023
  • Mathematica
    a[n_] := DivisorSum[n, (n/#)^# * Binomial[# + n, n] &]; Array[a, 30] (* Amiram Eldar, Jul 05 2023 *)
  • PARI
    a(n) = sumdiv(n, d, (n/d)^d*binomial(d+n, n));

Formula

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

A363668 a(n) = Sum_{d|n} (n/d)^d * binomial(d+n-1,d).

Original entry on oeis.org

1, 7, 19, 91, 151, 1135, 1765, 12355, 28846, 157917, 352837, 2280955, 5200469, 29986201, 80469589, 427061795, 1166803399, 6211188028, 17672632261, 89483074521, 271071666724, 1316291647997, 4116715364329, 19595444140771, 63205674328876, 292318539358879
Offset: 1

Views

Author

Seiichi Manyama, Jun 14 2023

Keywords

Crossrefs

Cf. A055225, A362683, A363639, A363640.
Cf. A343549, A363669.

Programs

  • Mathematica
    a[n_] := DivisorSum[n, (n/#)^# * Binomial[# + n - 1, #] &]; Array[a, 30] (* Amiram Eldar, Jul 12 2023 *)
  • PARI
    a(n) = sumdiv(n, d, (n/d)^d*binomial(d+n-1, d));

Formula

a(n) = [x^n] Sum_{k>0} (1/(1 - k*x^k)^n - 1).
Showing 1-5 of 5 results.

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