A258471 Number of partitions of 2n into two sorts of parts having exactly n parts of the second sort.

1, 3, 11, 41, 155, 590, 2258, 8677, 33454, 129335, 501180, 1945997, 7569223, 29487091, 115029830, 449288570, 1756808604, 6876430799, 26940317004, 105635470645, 414528962220, 1627841401281, 6396735649200, 25152046015693, 98955167336425, 389526824102747

Offset: 0

Author

Alois P. Heinz, May 31 2015

Keywords

• nonn

Links

• Alois P. Heinz, Table of n, a(n) for n = 0..300

Crossrefs

Cf. A256193.

Formula

a(n) = A256193(2n,n).

a(n) ~ c * 4^n / sqrt(Pi*n), where c = 1 / A048651 = 1 / Product_{k>=1} (1-1/2^k) = 3.462746619455... . - Vaclav Kotesovec, May 31 2015