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.

A293071 Square array A(n,k), n >= 0, k >= 0, read by antidiagonals, where column k is the expansion of g.f. Product_{i>0} Sum_{j=0..k} (-1)^j*j!*x^(j*i).

Original entry on oeis.org

1, 1, 0, 1, -1, 0, 1, -1, -1, 0, 1, -1, 1, 0, 0, 1, -1, 1, 0, 0, 0, 1, -1, 1, -6, 0, 1, 0, 1, -1, 1, -6, 0, -3, 0, 0, 1, -1, 1, -6, 24, 3, 4, 1, 0, 1, -1, 1, -6, 24, 3, 4, -3, 0, 0, 1, -1, 1, -6, 24, -117, -20, -3, 4, 0, 0, 1, -1, 1, -6, 24, -117, -20, -27, -8, -2
Offset: 0

Views

Author

Seiichi Manyama, Oct 03 2017

Keywords

Examples

			Square array begins:
   1,  1,  1,  1,  1, ...
   0, -1, -1, -1, -1, ...
   0, -1,  1,  1,  1, ...
   0,  0,  0, -6, -6, ...
   0,  0,  0,  0, 24, ...
   0,  1, -3,  3,  3, ...
		

Crossrefs

Columns k=0..5 give A000007, A010815, A293072, A293255, A293256, A293257.
Rows n=0 gives A000012.
Main diagonal gives A293236.
Cf. A293202.

Programs

  • Mathematica
    nmax = 12;
    col[k_] := CoefficientList[Product[Sum[(-1)^j j! x^(i j), {j, 0, k}], {i, 1, nmax+1}] + O[x]^(nmax+1), x]; M = PadRight[col[#], nmax+1]& /@ Range[0, nmax] // Transpose;
    A[n_, k_] := M[[n+1, k+1]];
    Table[A[n-k, k], {n, 0, nmax}, {k, n, 0, -1}] // Flatten (* Jean-François Alcover, Nov 15 2020 *)

A293204 G.f.: Product_{m>0} (1+x^m+2!*x^(2*m)).

Original entry on oeis.org

1, 1, 3, 2, 6, 7, 12, 13, 22, 26, 42, 46, 73, 80, 116, 139, 194, 226, 306, 358, 482, 558, 735, 856, 1108, 1300, 1657, 1926, 2426, 2834, 3530, 4110, 5082, 5898, 7234, 8409, 10216, 11860, 14304, 16568, 19891, 22990, 27470, 31670, 37630, 43382, 51274, 58982, 69450
Offset: 0

Views

Author

Seiichi Manyama, Oct 02 2017

Keywords

Examples

			Let's consider the partitions of n where no positive integer appears more than twice. (See A000726)
For n = 5,
    partition      |                         |
--------------------------------------------------------------
     5             -> one 5                  -> 1!       (= 1)
   = 4 + 1         -> one 4 and one 1        -> 1!*1!    (= 1)
   = 3 + 2         -> one 3 and one 2        -> 1!*1!    (= 1)
   = 3 + 1 + 1     -> one 3 and two 1        -> 1!*2!    (= 2)
   = 2 + 2 + 1     -> two 2 and one 1        -> 2!*1!    (= 2)
--------------------------------------------------------------
                                                a(5)      = 7.
For n = 6,
    partition      |                         |
--------------------------------------------------------------
     6             -> one 6                  -> 1!       (= 1)
   = 5 + 1         -> one 5 and one 1        -> 1!*1!    (= 1)
   = 4 + 2         -> one 4 and one 2        -> 1!*1!    (= 1)
   = 4 + 1 + 1     -> one 4 and two 1        -> 1!*2!    (= 2)
   = 3 + 3         -> two 3                  -> 2!       (= 2)
   = 3 + 2 + 1     -> one 3, one 2 and one 1 -> 1!*1!*1! (= 1)
   = 2 + 2 + 1 + 1 -> two 2 and two 1        -> 2!*2!    (= 4)
--------------------------------------------------------------
                                                a(6)      = 12.
		

Crossrefs

Column k=2 of A293202.
Cf. A293072.

Programs

  • Maple
    b:= proc(n, i) option remember; `if`(n=0, 1, `if`(i<1, 0,
          add(b(n-i*j, i-1)*j!, j=0..min(2, n/i))))
        end:
    a:= n-> b(n$2):
    seq(a(n), n=0..50);  # Alois P. Heinz, Oct 02 2017
  • Mathematica
    nmax = 100; CoefficientList[Series[Product[1 + x^k + 2*x^(2*k), {k, 1, nmax}], {x, 0, nmax}], x] (* Vaclav Kotesovec, Oct 02 2017 *)

Formula

a(n) ~ c^(1/4) * exp(2*sqrt(c*n)) / (4 * sqrt(Pi) * n^(3/4)), where c = Pi^2/3 - arctan(sqrt(7))^2 + log(2)^2/4 + polylog(2, -1/4 - I*sqrt(7)/4) + polylog(2, -1/4 + I*sqrt(7)/4) = 1.323865936864425754643630663383779192757247984691212163137... - Vaclav Kotesovec, Oct 02 2017
Equivalently, c = -polylog(2, -1/2 + I*sqrt(7)/2) - polylog(2, -1/2 - I*sqrt(7)/2). - Vaclav Kotesovec, Oct 05 2017

A293305 Square array A(n,k), n >= 0, k >= 0, read by antidiagonals, where column k is the expansion of g.f. Product_{i>0} (1 + Sum_{j=1..k} (-1)^j*j*x^(j*i)).

Original entry on oeis.org

1, 1, 0, 1, -1, 0, 1, -1, -1, 0, 1, -1, 1, 0, 0, 1, -1, 1, 0, 0, 0, 1, -1, 1, -3, 0, 1, 0, 1, -1, 1, -3, 0, -3, 0, 0, 1, -1, 1, -3, 4, 0, 4, 1, 0, 1, -1, 1, -3, 4, 0, 4, -3, 0, 0, 1, -1, 1, -3, 4, -5, 0, -3, 4, 0, 0, 1, -1, 1, -3, 4, -5, 0, -7, -2, -2, 0, 0, 1, -1, 1
Offset: 0

Views

Author

Seiichi Manyama, Oct 05 2017

Keywords

Examples

			Square array begins:
   1,  1,  1,  1,  1, ...
   0, -1, -1, -1, -1, ...
   0, -1,  1,  1,  1, ...
   0,  0,  0, -3, -3, ...
   0,  0,  0,  0,  4, ...
   0,  1, -3,  0,  0, ...
		

Crossrefs

Columns k=0..2 give A000007, A010815, A293072.
Rows n=0 gives A000012.
Main diagonal gives A293306.

Programs

  • Mathematica
    nmax = 12;
    col[k_] := col[k] = Product[1+Sum[(-1)^j*j*x^(i*j), {j, 1, k}], {i, 1, 2 nmax}] + O[x]^(2 nmax) // CoefficientList[#, x]&;
    A[n_, k_] := If[n == 0, 1, If[k == 0, 0, col[k][[n+1]]]];
    Table[A[n-k, k], {n, 0, nmax}, {k, n, 0, -1}] // Flatten (* Jean-François Alcover, Feb 21 2021 *)

A293304 Expansion of Product_{k>=1} (1 + x^(2*k-1) + 2*x^(4*k-2)).

Original entry on oeis.org

1, 1, 2, 1, 1, 3, 3, 5, 6, 4, 6, 8, 11, 13, 13, 18, 19, 23, 29, 32, 35, 40, 48, 51, 65, 78, 86, 96, 102, 121, 142, 162, 179, 199, 220, 251, 289, 323, 359, 395, 450, 499, 562, 631, 695, 762, 840, 952, 1055, 1167, 1292, 1413, 1557, 1733, 1903, 2112, 2323, 2534
Offset: 0

Views

Author

Vaclav Kotesovec, Oct 05 2017

Keywords

Crossrefs

Cf. A293072.

Programs

  • Mathematica
    nmax = 100; CoefficientList[Series[Product[(1 + x^(2*k-1) + 2*x^(4*k-2)), {k, 1, nmax}], {x, 0, nmax}], x]

Formula

a(n) ~ c^(1/4) * exp(sqrt(2*c*n)) / (2^(5/4) * sqrt(Pi) * n^(3/4)), where c = -polylog(2, -1/2 + I*sqrt(7)/2) - polylog(2, -1/2 - I*sqrt(7)/2) = 1.323865936864425754643630663383779192757247984691212163137...

A293294 G.f.: Product_{m>0} 1/(1 - x^m + 2!*x^(2*m)).

Original entry on oeis.org

1, 1, 0, -1, -1, 3, 3, -1, -8, -8, 12, 24, 5, -43, -55, 40, 137, 65, -215, -356, 97, 780, 624, -941, -2199, -260, 4052, 4638, -3536, -12861, -5676, 19858, 31449, -8337, -71220, -54243, 87733, 196679, 20733, -372807, -413794, 330731, 1159718, 497517, -1821469
Offset: 0

Views

Author

Seiichi Manyama, Oct 05 2017

Keywords

Crossrefs

Column k=2 of A293293.
Cf. A293072.

Programs

  • PARI
    nn = 50; Vec(prod(m=1, nn, 1/(1 - x^m + 2*x^(2*m))) + O(x^nn)) \\ Michel Marcus, Oct 05 2017

Formula

Convolution inverse of A293072.
Showing 1-5 of 5 results.