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 1-2 of 2 results.

A294653 Square array A(n,k), n >= 0, k >= 0, read by antidiagonals, where column k is the expansion of Product_{j>=1} (1-j^(k*j)*x^j) in powers of x.

Original entry on oeis.org

1, 1, -1, 1, -1, -1, 1, -1, -4, 0, 1, -1, -16, -23, 0, 1, -1, -64, -713, -229, 1, 1, -1, -256, -19619, -64807, -2761, 0, 1, -1, -1024, -531185, -16757533, -9688425, -42615, 1, 1, -1, -4096, -14347883, -4294435855, -30499541197, -2165979799, -758499, 0
Offset: 0

Views

Author

Seiichi Manyama, Nov 06 2017

Keywords

Examples

			Square array begins:
    1,    1,      1,         1,           1, ...
   -1,   -1,     -1,        -1,          -1, ...
   -1,   -4,    -16,       -64,        -256, ...
    0,  -23,   -713,    -19619,     -531185, ...
    0, -229, -64807, -16757533, -4294435855, ...
		

Crossrefs

Columns k=0..1 give A010815, A292312.
Rows n=0..2 give A000012, (-1)*A000012, (-1)*A000302.

Programs

  • Mathematica
    rows = 10;
    col[k_] := col[k] = CoefficientList[Product[(1 - j^(k*j)*x^j), {j, 1, rows + 3}] + O[x]^(rows + 3), x];
    A[n_, k_] := col[k][[n + 1]];
    (* or: *)
    A[0, ] = 1; A[n, k_] := A[n, k] = -(1/n)*Sum[DivisorSum[j, #^(1 + k*j) &]*A[n - j, k], {j, 1, n}];
    Table[A[n - k, k], {n, 0, rows - 1}, {k, n, 0, -1}] // Flatten (* Jean-François Alcover, Nov 10 2017 *)

Formula

A(0,k) = 1 and A(n,k) = -(1/n) * Sum_{j=1..n} (Sum_{d|j} d^(1+k*j)) * A(n-j,k) for n > 0.

A294950 Square array A(n,k), n >= 0, k >= 0, read by antidiagonals, where column k is the expansion of Product_{j>=1} 1/(1-j^(k*j)*x^j)^j in powers of x.

Original entry on oeis.org

1, 1, 1, 1, 1, 3, 1, 1, 9, 6, 1, 1, 33, 90, 13, 1, 1, 129, 2220, 1162, 24, 1, 1, 513, 59178, 265132, 17435, 48, 1, 1, 2049, 1594836, 67180330, 49163241, 310193, 86, 1, 1, 8193, 43048770, 17181660628, 152662629227, 13121450895, 6286826, 160
Offset: 0

Views

Author

Seiichi Manyama, Nov 12 2017

Keywords

Examples

			Square array begins:
    1,     1,        1,            1,               1, ...
    1,     1,        1,            1,               1, ...
    3,     9,       33,          129,             513, ...
    6,    90,     2220,        59178,         1594836, ...
   13,  1162,   265132,     67180330,     17181660628, ...
   24, 17435, 49163241, 152662629227, 476855156157129, ...
		

Crossrefs

Columns k=0..2 give A000219, A294813, A294954.
Rows n=0+1, 2 give A000012, A087289.

Formula

A(0,k) = 1 and A(n,k) = (1/n) * Sum_{j=1..n} (Sum_{d|j} d^(2+k*j)) * A(n-j,k) for n > 0.
Showing 1-2 of 2 results.