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 1-4 of 4 results.

A269129 Number A(n,k) of sequences with k copies each of 1,2,...,n avoiding the pattern 12...n; square array A(n,k), n>=0, k>=0, read by antidiagonals.

Original entry on oeis.org

0, 0, 1, 0, 0, 1, 0, 0, 1, 1, 0, 0, 1, 5, 1, 0, 0, 1, 43, 23, 1, 0, 0, 1, 374, 1879, 119, 1, 0, 0, 1, 3199, 173891, 102011, 719, 1, 0, 0, 1, 26945, 16140983, 117392909, 7235651, 5039, 1, 0, 0, 1, 224296, 1474050783, 142951955371, 117108036719, 674641325, 40319, 1
Offset: 0

Views

Author

Alois P. Heinz, Feb 19 2016

Keywords

Examples

			Square array A(n,k) begins:
  0,   0,      0,         0,            0,               0, ...
  1,   0,      0,         0,            0,               0, ...
  1,   1,      1,         1,            1,               1, ...
  1,   5,     43,       374,         3199,           26945, ...
  1,  23,   1879,    173891,     16140983,      1474050783, ...
  1, 119, 102011, 117392909, 142951955371, 173996758190594, ...
		

Crossrefs

Programs

  • Maple
    g:= proc(l) option remember; (n-> f(l[1..nops(l)-1])*
          binomial(n-1, l[-1]-1)+add(f(sort(subsop(j=l[j]
          -1, l))), j=1..nops(l)-1))(add(i, i=l))
        end:
    f:= l->(n->`if`(n=0, 1, `if`(l[1]=0, 0, `if`(n=1 or l[-1]=1, 1,
        `if`(n=2, binomial(l[1]+l[2], l[1])-1, g(l))))))(nops(l)):
    A:= (n, k)-> (k*n)!/k!^n - f([k$n]):
    seq(seq(A(n, d-n), n=0..d), d=0..12);
    # second Maple program:
    b:= proc(k, p, j, l, t) option remember;
          `if`(k=0, (-1)^t/l!, `if`(p<0, 0, add(b(k-i, p-1,
           j+1, l+i*j, irem(t+i*j, 2))/(i!*p!^i), i=0..k)))
        end:
    A:= (n, k)-> (n*k)!*(1/k!^n-b(n, k-1, 1, 0, irem(n, 2))*n!):
    seq(seq(A(n, d-n), n=0..d), d=0..12);  # Alois P. Heinz, Mar 03 2016
  • Mathematica
    b[k_, p_, j_, l_, t_] := b[k, p, j, l, t] = If[k == 0, (-1)^t/l!, If[p < 0, 0, Sum[b[k-i, p-1, j+1, l + i j, Mod[t + i j, 2]]/(i! p!^i), {i, 0, k}]] ];
    A[n_, k_] := (n k)! (1/k!^n - b[n, k-1, 1, 0, Mod[n, 2]] n!); Table[ Table[ A[n, d-n], {n, 0, d}], {d, 0, 12}] // Flatten (* Jean-François Alcover, Apr 07 2016, after Alois P. Heinz *)

Formula

A(n,k) = A089759(k,n) - A047909(k,n) = A187783(n,k) - A047909(k,n).

A267479 Number A(n,k) of words on {1,1,2,2,...,n,n} with longest increasing subsequence of length <= k; square array A(n,k), n>=0, k>=0, read by antidiagonals.

Original entry on oeis.org

1, 1, 0, 1, 1, 0, 1, 1, 1, 0, 1, 1, 6, 1, 0, 1, 1, 6, 43, 1, 0, 1, 1, 6, 90, 352, 1, 0, 1, 1, 6, 90, 1879, 3114, 1, 0, 1, 1, 6, 90, 2520, 47024, 29004, 1, 0, 1, 1, 6, 90, 2520, 102011, 1331664, 280221, 1, 0, 1, 1, 6, 90, 2520, 113400, 5176504, 41250519, 2782476, 1, 0
Offset: 0

Views

Author

Alois P. Heinz, Jan 15 2016

Keywords

Examples

			Square array A(n,k) begins:
  1, 1,     1,       1,       1,       1,       1, ...
  0, 1,     1,       1,       1,       1,       1, ...
  0, 1,     6,       6,       6,       6,       6, ...
  0, 1,    43,      90,      90,      90,      90, ...
  0, 1,   352,    1879,    2520,    2520,    2520, ...
  0, 1,  3114,   47024,  102011,  113400,  113400, ...
  0, 1, 29004, 1331664, 5176504, 7235651, 7484400, ...
		

Crossrefs

Columns k=0-4 give: A000007, A000012, A220097, A266734, A266735.
Main diagonal gives A000680.
First lower diagonal gives A267532.

Formula

A(n,k) = Sum_{i=0..k} A267480(n,i).

A267480 Number T(n,k) of words on {1,1,2,2,...,n,n} with longest increasing subsequence of length k; triangle T(n,k), n>=0, 0<=k<=n, read by rows.

Original entry on oeis.org

1, 0, 1, 0, 1, 5, 0, 1, 42, 47, 0, 1, 351, 1527, 641, 0, 1, 3113, 43910, 54987, 11389, 0, 1, 29003, 1302660, 3844840, 2059147, 248749, 0, 1, 280220, 40970298, 265777225, 285588543, 82025038, 6439075, 0, 1, 2782475, 1364750889, 19104601915, 37783672691, 19773928713, 3507289363, 192621953
Offset: 0

Views

Author

Alois P. Heinz, Jan 15 2016

Keywords

Examples

			Triangle T(n,k) begins:
  1;
  0, 1;
  0, 1,      5;
  0, 1,     42,       47;
  0, 1,    351,     1527,       641;
  0, 1,   3113,    43910,     54987,     11389;
  0, 1,  29003,  1302660,   3844840,   2059147,   248749;
  0, 1, 280220, 40970298, 265777225, 285588543, 82025038, 6439075;
		

Crossrefs

Main diagonal gives A006902.
Row sums give A000680.

Formula

T(n,0) = A267479(n,0), T(n,k) = A267479(n,k) - A267479(n,k-1) for k>0.
Sum_{k=0..n-1} T(n,k) = A267532(n).

A269042 Number of permutations of [2n] avoiding the pattern 12...n.

Original entry on oeis.org

0, 0, 1, 132, 15767, 2190688, 370531683, 77182248916, 19835792076675, 6266271456118776, 2413632612087046844, 1120958514818713738544, 619918692943471064695593, 403190647991638511052901232, 304867528413299672718870216538, 265248225675908889875489731636920
Offset: 0

Views

Author

Alois P. Heinz, Feb 18 2016

Keywords

Examples

			a(2) = 1: 4321.
a(3) = 132: 165432, 216543, 261543, 265143, 265413, 265431, 316542, ..., 653412, 653421, 654132, 654213, 654231, 654312, 654321.
		

Crossrefs

Programs

  • Maple
    h:= proc(l) (n-> add(i, i=l)!/mul(mul(1+l[i]-j+add(`if`(
          l[k]>=j, 1, 0), k=i+1..n), j=1..l[i]), i=1..n))(nops(l))
        end:
    g:= (n, i, l)-> `if`(n=0 or i=1, h([l[], 1$n])^2, `if`(i<1, 0,
                     add(g(n-i*j, i-1, [l[], i$j]), j=0..n/i))):
    a:= n-> `if`(n=0, 0, g(2*n, n-1, [])):
    seq(a(n), n=0..15);
  • Mathematica
    h[l_] := Function[n, Total[l]!/Product[Product[1+l[[i]]-j+Sum[If[l[[k]] >= j, 1, 0], { k, i+1, n}], {j, 1, l[[i]]}], {i, 1, n}]][Length[l]];
    g[n_, i_, l_] := If[n == 0 || i == 1, h[Join[l, Table[1, {n}]]]^2, If[i < 1, 0, Sum[g[n - i*j, i-1, Join[l, Table[i, {j}]]], {j, 0, n/i}]]];
    a[n_] := If[n == 0, 0, g[2n, n-1, {}]];
    Table[a[n], {n, 0, 15}] (* Jean-François Alcover, Apr 01 2017, translated from Maple *)

Formula

a(n) = (2n)! - A269021(n).
a(n) = A214015(2n,n-1) for n>0.
a(n) ~ (2*n)!. - Vaclav Kotesovec, Mar 26 2016
Showing 1-4 of 4 results.