A026921 Triangular array E by rows: E(n,k) = number of partitions of n into an even number of parts, the greatest being k.

0, 1, 0, 0, 1, 0, 1, 1, 1, 0, 0, 1, 1, 1, 0, 1, 1, 2, 1, 1, 0, 0, 2, 1, 2, 1, 1, 0, 1, 2, 3, 2, 2, 1, 1, 0, 0, 2, 3, 3, 2, 2, 1, 1, 0, 1, 2, 5, 4, 4, 2, 2, 1, 1, 0, 0, 3, 4, 6, 4, 4, 2, 2, 1, 1, 0, 1, 3, 7, 7, 7, 5, 4, 2, 2, 1, 1, 0, 0, 3, 6, 10, 8, 7, 5, 4, 2, 2, 1, 1, 0, 1, 3, 9, 11, 13, 9, 8, 5, 4, 2, 2, 1, 1, 0

Offset: 1

Author

Clark Kimberling

Keywords

• nonn
• tabl

Comments

The reversed rows (see example) stabilize to A027193. [Joerg Arndt, May 12 2013]

Examples

			G.f. = (1)*q^0 +
(0) * q^1 +
(1 + 0*z) * q^2 +
(0 + 1*z + 0*z^2) * q^3 +
(1 + 1*z + 1*z^2 + 0*z^3) * q^4 +
(0 + 1*z + 1*z^2 + 1*z^3 + 0*z^4) * q^5 +
(1 + 1*z + 2*z^2 + 1*z^3 + 1*z^4 + 0*z^5) * q^6 +
(0 + 2*z + 1*z^2 + 2*z^3 + 1*z^4 + 1*z^5 + 0*z^6) * q^7 +
... [_Joerg Arndt_, May 12 2013]
Triangle starts:
01: [0]
02: [1, 0]
03: [0, 1, 0]
04: [1, 1, 1, 0]
05: [0, 1, 1, 1, 0]
06: [1, 1, 2, 1, 1, 0]
07: [0, 2, 1, 2, 1, 1, 0]
08: [1, 2, 3, 2, 2, 1, 1, 0]
09: [0, 2, 3, 3, 2, 2, 1, 1, 0]
10: [1, 2, 5, 4, 4, 2, 2, 1, 1, 0]
11: [0, 3, 4, 6, 4, 4, 2, 2, 1, 1, 0]
12: [1, 3, 7, 7, 7, 5, 4, 2, 2, 1, 1, 0]
13: [0, 3, 6, 10, 8, 7, 5, 4, 2, 2, 1, 1, 0]
14: [1, 3, 9, 11, 13, 9, 8, 5, 4, 2, 2, 1, 1, 0]
15: [0, 4, 8, 14, 14, 14, 9, 8, 5, 4, 2, 2, 1, 1, 0]
16: [1, 4, 12, 16, 20, 17, 15, 10, 8, 5, 4, 2, 2, 1, 1, 0]
17: [0, 4, 11, 20, 22, 23, 18, 15, 10, 8, 5, 4, 2, 2, 1, 1, 0]
18: [1, 4, 15, 23, 30, 28, 26, 19, 16, 10, 8, 5, 4, 2, 2, 1, 1, 0]
19: [0, 5, 13, 28, 33, 37, 31, 27, 19, 16, 10, 8, 5, 4, 2, 2, 1, 1, 0]
20: [1, 5, 18, 31, 44, 44, 43, 34, 28, 20, 16, 10, 8, 5, 4, 2, 2, 1, 1, 0]
... [_Joerg Arndt_, May 12 2013]
		

Crossrefs

E(n, k) = O(n-k, 1)+O(n-k, 2)+...+O(n-k, m), where m=MIN{k, n-k}, n >= 2, O given by A026920.

Columns k=3..6: A026927, A026928, A026929, A026930.

Programs

PARI

N = 20;  q = 'q + O('q^N);
gf = sum(n=0,N, q^(2*n)/prod(k=1, 2*n, 1-'z*q^k) );
v = Vec(gf);
{ for(n=2, #v, /* print triangle starting with row 1: */
    p = Pol('c0 +'cn*'z^n + v[n],'z);
    p = polrecip(p);
    p = Vec(p);
    p[1] -= 'c0;
    p = vector(#p-2, j, p[j]);
    print(p);
); }
/* Joerg Arndt, May 12 2013 */

Formula

G.f. (including term a(0)=1): sum(n>=0, q^(2*n)/prod(k=1..2*n, 1-z*q^k) ), set z=1 to obtain g.f. for A027187. [Joerg Arndt, May 12 2013]

A026920(n,k) + E(n,k) = A008284(n,k). - R. J. Mathar, Aug 23 2019