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.

A334622 A(n,k) is the sum of the k-th powers of the descent set statistics for permutations of [n]; square array A(n,k), n>=0, k>=0, read by antidiagonals.

Original entry on oeis.org

1, 1, 1, 1, 1, 2, 1, 1, 2, 4, 1, 1, 2, 6, 8, 1, 1, 2, 10, 24, 16, 1, 1, 2, 18, 88, 120, 32, 1, 1, 2, 34, 360, 1216, 720, 64, 1, 1, 2, 66, 1576, 14460, 24176, 5040, 128, 1, 1, 2, 130, 7224, 190216, 994680, 654424, 40320, 256, 1, 1, 2, 258, 34168, 2675100, 46479536, 109021500, 23136128, 362880, 512
Offset: 0

Views

Author

Alois P. Heinz, Sep 09 2020

Keywords

Examples

			Square array A(n,k) begins:
   1,   1,     1,      1,        1,          1,            1, ...
   1,   1,     1,      1,        1,          1,            1, ...
   2,   2,     2,      2,        2,          2,            2, ...
   4,   6,    10,     18,       34,         66,          130, ...
   8,  24,    88,    360,     1576,       7224,        34168, ...
  16, 120,  1216,  14460,   190216,    2675100,     39333016, ...
  32, 720, 24176, 994680, 46479536, 2368873800, 128235838496, ...
  ...
		

Crossrefs

Columns k=0-4 give: A011782, A000142, A060350, A291902, A291903.
Rows n=0+1, 2-3 give: A000012, A007395(k+1), A052548(k+1).
Main diagonal gives A334623.

Programs

  • Maple
    b:= proc(u, o, t) option remember; expand(`if`(u+o=0, 1,
          add(b(u-j, o+j-1, t+1)*x^floor(2^(t-1)), j=1..u)+
          add(b(u+j-1, o-j, t+1), j=1..o)))
        end:
    A:= (n, k)-> (p-> add(coeff(p, x, i)^k, i=0..degree(p)))(b(n, 0$2)):
    seq(seq(A(n, d-n), n=0..d), d=0..10);
  • Mathematica
    b[u_, o_, t_] := b[u, o, t] = Expand[If[u + o == 0, 1,
        Sum[b[u - j, o + j - 1, t + 1] x^Floor[2^(t - 1)], {j, 1, u}] +
        Sum[b[u + j - 1, o - j, t + 1], {j, 1, o}]]];
    A[n_, k_] := Function[p, Sum[Coefficient[p, x, i]^k, {i, 0, Exponent[p, x]}]][b[n, 0, 0]];
    Table[Table[A[n, d - n], {n, 0, d}], {d, 0, 10}] // Flatten (* Jean-François Alcover, Dec 20 2020, after Alois P. Heinz *)

Formula

A(n,k) = Sum_{j=0..ceiling(2^(n-1))-1} A060351(n,j)^k.

A168562 Sum of squares of Eulerian numbers in row n of triangle A008292 with a(0)=1.

Original entry on oeis.org

1, 1, 2, 18, 244, 5710, 188908, 8702820, 524888040, 40393084950, 3853034107900, 446671026849916, 61824801560228056, 10072685383683311116, 1907978676359896992824, 415795605119514578204616, 103294156408291202467520976, 29018125910193347265466916070
Offset: 0

Views

Author

Paul D. Hanna, Nov 29 2009

Keywords

Comments

Row sums of Eulerian triangle A008292 yield the factorials.

Examples

			a(1) = 1 = 1;
a(2) = 1 + 1 = 2;
a(3) = 1 + 4^2 + 1 = 18;
a(4) = 1 + 11^2 + 11^2 + 1 = 244;
a(5) = 1 + 26^2 + 66^2 + 26^2 + 1 = 5710;
a(6) = 1 + 57^2 + 302^2 + 302^2 + 57^2 + 1 = 188908.
		

Crossrefs

Cf. A008292.
Column k=2 of A335545.

Programs

  • Maple
    a:= n-> add(combinat[eulerian1](n, k)^2, k=0..n):
    seq(a(n), n=0..18);  # Alois P. Heinz, Sep 10 2020
  • PARI
    {a(n)=sum(k=0,n,sum(j=0, k, (-1)^j*(k-j)^n*binomial(n+1, j))^2)}

Formula

a(n) = Sum_{k=0..n} [ Sum_{j=0..k} (-1)^j*(k-j)^n*C(n+1, j) ]^2.

A335546 Sum of the n-th powers of the (positive) number of permutations of [n] with j descents (j=0..max(0,n-1)).

Original entry on oeis.org

1, 1, 2, 66, 29284, 1276095330, 1517369276209828, 487282023126556473747120, 7083859535826403131254334882236808, 55967865856667137512789954604119317025544887810, 29848842646338160810499934016489864718841567718650088748120500
Offset: 0

Views

Author

Alois P. Heinz, Sep 12 2020

Keywords

Crossrefs

Main diagonal of A335545.

Programs

  • Mathematica
    B[n_, k_] := Sum[(-1)^j Binomial[n+1, j] (k-j+1)^n, {j, 0, k+1}];
    a[n_] := If[n == 0, 1, Sum[B[n, j]^n, {j, 0, n-1}]];
    Table[a[n], {n, 0, 10}] (* Jean-François Alcover, Sep 03 2021, from A335545 *)

Formula

a(n) = A335545(n,n).
a(n) = Sum_{j=0..n} A173018(n,j)^n.
Showing 1-3 of 3 results.