A241543 a(n) = A241477(n, n).

1, 1, 2, 2, 2, 6, 4, 20, 10, 70, 28, 252, 84, 924, 264, 3432, 858, 12870, 2860, 48620, 9724, 184756, 33592, 705432, 117572, 2704156, 416024, 10400600, 1485800, 40116600, 5348880, 155117520, 19389690, 601080390, 70715340, 2333606220, 259289580, 9075135300

Offset: 0

Author

Peter Luschny, Apr 25 2014

Keywords

• nonn

Comments

See A241477 and A232500 for the combinatorial definitions.

Crossrefs

Cf. A057977, A241477, A232500.

Programs

Maple

A241543 := proc(n)
    if n < 2 then 1
  else 2*iquo(n,2)*(n-2)!/iquo(n,2)!^2
    fi end:
seq(A241543(n), n=0..37);

Formula

a(n) = 2*floor(n/2)*(n-2)!/floor(n/2)!^2 for n>=2.

a(n+2) = 2*A057977(n) for n>=0. - Peter Luschny, Jul 17 2016