A006523 Sum ((-1)^(i+1)*binomial(n,i)*2^i*(2*n-1)!,i=1..n) for n odd.

2, 240, 725760, 12454041600, 711374856192000, 102181884343418880000, 31022420086661971968000000, 17683523987479403909087232000000, 17366635237623772991036388802560000000, 27527506182452690092631959163161804800000000

Offset

1,1

Links

Table of n, a(n) for n=1..10.

Formula

a(n) = 2*(4*n-3)!. - Christian Krause, Oct 08 2023

Prog

(PARI) a(n) = n=2*n-1; sum(i=1, n, (-1)^(i+1)*binomial(n, i)*2^i*(2*n-1)!); \\ Michel Marcus, Oct 08 2023

Crossrefs

Cf. A000142.

Sequence in context: A217972 A071967 A024348 * A294319 A055968 A068838

Adjacent sequences: A006520 A006521 A006522 * A006524 A006525 A006526

Keyword

nonn

Author

N. J. A. Sloane

Status

approved