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 21-27 of 27 results.

A284993 Square array A(n,k), n>=0, k>=0, read by antidiagonals, where column k is the expansion of Product_{j>=1} 1/(1+x^j)^(j^k) in powers of x.

Original entry on oeis.org

1, 1, -1, 1, -1, 0, 1, -1, -1, -1, 1, -1, -3, -2, 1, 1, -1, -7, -6, 1, -1, 1, -1, -15, -20, 0, 0, 1, 1, -1, -31, -66, -8, 11, 4, -1, 1, -1, -63, -212, -54, 99, 42, 2, 2, 1, -1, -127, -666, -284, 725, 455, 63, 8, -2, 1, -1, -255, -2060, -1350, 4935, 4580, 958, 73
Offset: 0

Views

Author

Seiichi Manyama, Apr 07 2017

Keywords

Examples

			Square array begins:
   1,  1,  1,   1,   1,    1, ...
  -1, -1, -1,  -1,  -1,   -1, ...
   0, -1, -3,  -7, -15,  -31, ...
  -1, -2, -6, -20, -66, -212, ...
   1,  1,  0,  -8, -54, -284, ...
		

Crossrefs

Columns k=0-5 give A081362, A255528, A284896, A284897, A284898, A284899.

Formula

G.f. of column k: Product_{j>=1} 1/(1+x^j)^(j^k).

A319107 Expansion of Product_{k>=1} (1 + x^k)^(sigma_1(k)-k), where sigma_1(k) = sum of divisors of k (A000203).

Original entry on oeis.org

1, 0, 1, 1, 3, 2, 9, 5, 17, 17, 38, 33, 88, 75, 169, 181, 343, 353, 712, 728, 1348, 1518, 2591, 2898, 5025, 5615, 9259, 10866, 17160, 20111, 31775, 37264, 57130, 68782, 102663, 123698, 183793, 221708, 323077, 395325, 566079, 693248, 987086, 1210110, 1700074, 2100674, 2915549
Offset: 0

Views

Author

Ilya Gutkovskiy, Sep 10 2018

Keywords

Comments

Convolution of A192065 and A255528.
Weigh transform of A001065.

Crossrefs

Programs

  • Maple
    with(numtheory): a:=series(mul((1+x^k)^(sigma(k)-k),k=1..100),x=0,47): seq(coeff(a,x,n),n=0..46); # Paolo P. Lava, Apr 02 2019
  • Mathematica
    nmax = 46; CoefficientList[Series[Product[(1 + x^k)^(DivisorSigma[1, k] - k), {k, 1, nmax}], {x, 0, nmax}], x]
    nmax = 46; CoefficientList[Series[Exp[Sum[Sum[(-1)^(k/d + 1) d (DivisorSigma[1, d] - d), {d, Divisors[k]}] x^k/k, {k, 1, nmax}]], {x, 0, nmax}], x]
    a[n_] := a[n] = If[n == 0, 1, Sum[Sum[(-1)^(k/d + 1) d (DivisorSigma[1, d] - d), {d, Divisors[k]}] a[n - k], {k, 1, n}]/n]; Table[a[n], {n, 0, 46}]

Formula

G.f.: Product_{k>=1} (1 + x^k)^A001065(k).
G.f.: exp(Sum_{k>=1} ( Sum_{d|k} (-1)^(k/d+1)*d*(sigma_1(d) - d) ) * x^k/k).
a(n) ~ exp(-Pi^4 / (864*(Pi^2 - 6)*Zeta(3)) - Pi^2 * n^(1/3) / (12*(2*(Pi^2 - 6)*Zeta(3))^(1/3)) + 3*((Pi^2 - 6)*Zeta(3))^(1/3) * n^(2/3) / 2^(5/3)) * ((Pi^2 - 6)*Zeta(3))^(1/6) / (2^(17/24) * sqrt(3*Pi) * n^(2/3)). - Vaclav Kotesovec, Sep 11 2018

A268501 Expansion of Product_{k>=1} ((1 + k*x^k) / (1 + x^k))^k.

Original entry on oeis.org

1, 0, 2, 6, 11, 32, 60, 148, 279, 690, 1312, 2778, 5684, 11282, 22920, 44724, 87919, 168978, 329800, 623086, 1189794, 2235744, 4189442, 7795642, 14438670, 26577246, 48616050, 88724110, 160629612, 290267100, 521225220, 933031364, 1661954928, 2950946220
Offset: 0

Views

Author

Vaclav Kotesovec, Feb 06 2016

Keywords

Crossrefs

Programs

  • Mathematica
    nmax = 50; CoefficientList[Series[Product[((1+k*x^k)/(1+x^k))^k, {k, 1, nmax}], {x, 0, nmax}], x]

A305628 Expansion of Product_{k>=1} 1/(1 + x^k)^(k+1).

Original entry on oeis.org

1, -2, 0, -2, 5, -2, 7, -6, 11, -20, 13, -32, 31, -50, 60, -70, 124, -112, 192, -198, 295, -364, 422, -616, 661, -1002, 1034, -1500, 1737, -2208, 2808, -3234, 4462, -4876, 6735, -7464, 9990, -11610, 14410, -17866, 20947, -27082, 30493, -40056, 45147, -58196, 66999, -83278, 99641
Offset: 0

Views

Author

Ilya Gutkovskiy, Aug 11 2018

Keywords

Comments

Convolution of A081362 and A255528.
Convolution inverse of A219555.

Crossrefs

Programs

  • Mathematica
    nmax = 48; CoefficientList[Series[Product[1/(1 + x^k)^(k + 1), {k, 1, nmax}], {x, 0, nmax}], x]
    nmax = 48; CoefficientList[Series[Exp[Sum[(-1)^k x^k (2 - x^k)/(k (1 - x^k)^2), {k, 1, nmax}]], {x,0, nmax}], x]
    a[n_] := a[n] = If[n == 0, 1, Sum[Sum[(-1)^(k/d) d (d + 1), {d, Divisors[k]}] a[n - k], {k, 1, n}]/n]; Table[a[n], {n, 0, 48}]

Formula

G.f.: exp(Sum_{k>=1} (-1)^k*x^k*(2 - x^k)/(k*(1 - x^k)^2)).
a(n) ~ (-1)^n * exp(3 * Zeta(3)^(1/3) * n^(2/3) / 2^(5/3) + Pi^2 * n^(1/3) / (3 * 2^(7/3) * Zeta(3)^(1/3)) - 1/12 - Pi^4 / (864 * Zeta(3))) * A * Zeta(3)^(5/36) / (2^(7/9) * sqrt(3*Pi) * n^(23/36)), where A is the Glaisher-Kinkelin constant A074962. - Vaclav Kotesovec, Aug 21 2018

A301831 G.f. A(x) satisfies: A(x) = Product_{k>=1} 1/(1 + x^k*A(x)^k)^k.

Original entry on oeis.org

1, -1, 0, 0, 6, -16, 16, -34, 217, -681, 1343, -3466, 13370, -42380, 109477, -312448, 1040248, -3267138, 9447529, -28367596, 90504001, -283611105, 861087913, -2654231074, 8386506600, -26359974392, 81902319183, -256179313766, 809890745232, -2557697524240, 8046530976599
Offset: 0

Views

Author

Ilya Gutkovskiy, Mar 27 2018

Keywords

Examples

			G.f. A(x) = 1 - x + 6*x^4 - 16*x^5 + 16*x^6 - 34*x^7 + 217*x^8 - 681*x^9 + 1343*x^10 - 3466*x^11 + ...
log(A(x)) = -x - x^2/2 - x^3/3 + 23*x^4/4 - 51*x^5/5 + 35*x^6/6 - 197*x^7/7 + ... + A281266(n)*x^n/n + ...
		

Crossrefs

Formula

G.f. satisfies: A(x) = exp(Sum_{k>=1} (-1)^k*x^k*A(x)^k/(k*(1 - x^k*A(x)^k)^2)).
a(n) = [x^n] (Sum_{k>=0} A255528(k)*x^k)^(n+1)/(n + 1).

A305255 a(n) = [x^n] exp(Sum_{k>=1} (-1)^k*x^k/(k*(1 - x^k)^n)).

Original entry on oeis.org

1, -1, -1, -4, -3, 14, 240, 1686, 9479, 36761, 3412, -1951731, -27296124, -268495319, -2093667873, -11586874946, -3788945531, 1127535019748, 21900095232973, 297591401221473, 3270627818325128, 28116733997044842, 129815302615081267, -1568168714539146596, -59839621829784309343
Offset: 0

Views

Author

Ilya Gutkovskiy, May 28 2018

Keywords

Crossrefs

Programs

  • Mathematica
    Table[SeriesCoefficient[Exp[Sum[(-1)^k x^k/(k (1 - x^k)^n), {k, 1, n}]], {x, 0, n}], {n, 0, 24}]
    Table[SeriesCoefficient[Product[1/(1 + x^k)^Binomial[n + k - 2, n - 1], {k, 1, n}], {x, 0, n}], {n, 0, 24}]

Formula

a(n) = [x^n] Product_{k>=1} 1/(1 + x^k)^binomial(n+k-2,n-1).

A319109 Expansion of Product_{k>=1} 1/(1 + x^k)^(k-1).

Original entry on oeis.org

1, 0, -1, -2, -2, -2, 0, 2, 7, 8, 12, 10, 9, -2, -10, -32, -40, -62, -62, -70, -37, -20, 57, 106, 224, 272, 388, 376, 431, 272, 192, -184, -414, -1012, -1321, -2020, -2157, -2700, -2318, -2352, -1014, -272, 2280, 3798, 7464, 9200, 13257, 13958, 17098, 14846, 15266
Offset: 0

Views

Author

Ilya Gutkovskiy, Sep 10 2018

Keywords

Comments

Convolution of A000009 and A255528.
Convolution inverse of A052812.

Crossrefs

Programs

  • Maple
    a:=series(mul(1/(1+x^k)^(k-1),k=1..100),x=0,51): seq(coeff(a,x,n),n=0..50); # Paolo P. Lava, Apr 02 2019
  • Mathematica
    nmax = 50; CoefficientList[Series[Product[1/(1 + x^k)^(k - 1), {k, 1, nmax}], {x, 0, nmax}], x]
    nmax = 50; CoefficientList[Series[Exp[Sum[(-1)^k x^(2 k)/(k (1 - x^k)^2), {k, 1, nmax}]], {x, 0, nmax}], x]
    a[n_] := a[n] = If[n == 0, 1, Sum[Sum[(-1)^(k/d) d (d - 1), {d, Divisors[k]}] a[n - k], {k, 1, n}]/n]; Table[a[n], {n, 0, 50}]

Formula

G.f.: exp(Sum_{k>=1} (-1)^k*x^(2*k)/(k*(1 - x^k)^2)).
Previous Showing 21-27 of 27 results.