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 1-3 of 3 results.

A293532 E.g.f.: exp(x/(x^2 - 1)).

Original entry on oeis.org

1, -1, 1, -7, 25, -181, 1201, -10291, 97777, -1013545, 12202561, -151573951, 2173233481, -31758579997, 524057015665, -8838296029291, 164416415570401, -3145357419120721, 65057767274601217, -1391243470549894135, 31671795881695430521, -747996624368605997701
Offset: 0

Views

Author

Seiichi Manyama, Oct 11 2017

Keywords

Crossrefs

Column k=2 of A293530.
Cf. A088009.

Programs

  • Mathematica
    CoefficientList[Series[E^(x/(x^2 - 1)), {x, 0, 20}], x] * Range[0, 20]! (* Vaclav Kotesovec, Oct 12 2017 *)
  • PARI
    N=66; x='x+O('x^N); Vec(serlaplace(exp(x/(x^2-1))))

Formula

E.g.f.: Product_{k>=1} 1/(1 + x^k)^(phi(k)/k), where phi() is the Euler totient function (A000010). - Ilya Gutkovskiy, May 25 2019

A293525 Square array A(n,k), n >= 0, k >= 1, read by antidiagonals, where column k is the expansion of e.g.f. Product_{j > 0, j mod k > 0} exp(x^j).

Original entry on oeis.org

1, 1, 0, 1, 1, 0, 1, 1, 1, 0, 1, 1, 3, 7, 0, 1, 1, 3, 7, 25, 0, 1, 1, 3, 13, 49, 181, 0, 1, 1, 3, 13, 49, 321, 1201, 0, 1, 1, 3, 13, 73, 381, 2131, 10291, 0, 1, 1, 3, 13, 73, 381, 2971, 19783, 97777, 0, 1, 1, 3, 13, 73, 501, 3331, 26713, 195777, 1013545, 0, 1, 1
Offset: 0

Views

Author

Seiichi Manyama, Oct 11 2017

Keywords

Examples

			Square array begins:
   1,   1,   1,   1,   1, ...
   0,   1,   1,   1,   1, ...
   0,   1,   3,   3,   3, ...
   0,   7,   7,  13,  13, ...
   0,  25,  49,  49,  73, ...
   0, 181, 321, 381, 381, ...
		

Crossrefs

Columns k=1..3 give A000007, A088009, A113775.
Rows n=0 gives A000012.
Main diagonal gives A000262.
Cf. A293530.

Programs

  • Mathematica
    kmax = 12; col[k_] := PadRight[(Exp[Sum[x^j, {j, 1, k - 1}]/(1 - x^k)] + O[x]^kmax // CoefficientList[#, x] &), kmax]*Range[0, kmax - 1]!; A = Array[col, kmax]; Table[A[[n - k + 1, k]], {n, 1, kmax}, {k, 1, n}] // Flatten (* Jean-François Alcover, Oct 12 2017, from formula *)

Formula

E.g.f. of column k: exp((Sum_{j=1..k-1} x^j)/(1 - x^k)).

A293533 E.g.f.: 1/Product_{m > 0, m mod 3 > 0} exp(x^m).

Original entry on oeis.org

1, -1, -1, 5, -23, -41, 1111, -6259, -16015, 828143, -6453809, -23557931, 1516982809, -15821700025, -76745280793, 5613303472349, -73951449390239, -445513157340449, 36776986711862815, -582726291386478427, -4158268555818657079, 388618610293537423799
Offset: 0

Views

Author

Seiichi Manyama, Oct 11 2017

Keywords

Crossrefs

Column k=3 of A293530.

Programs

  • Mathematica
    CoefficientList[Series[E^(x*(1 + x)/(x^3 - 1)), {x, 0, 20}], x] * Range[0, 20]! (* Vaclav Kotesovec, Oct 12 2017 *)
  • PARI
    N=66; x='x+O('x^N); Vec(serlaplace(exp((x+x^2)/(x^3-1))))
    
  • PARI
    N=66; x='x+O('x^N); Vec(serlaplace(prod(m=1, N, exp(x^(3*m))/exp(x^m))))

Formula

E.g.f.: exp((x + x^2)/(x^3 - 1)).
Showing 1-3 of 3 results.