A024421 a(n) = n!*(1/C(n,0) - 1/C(n,1) - ... - 1/C(n,[ n/2 ])).

1, 1, 1, 4, 14, 84, 516, 3936, 32544, 305280, 3123360, 35112960, 427559040, 5629236480, 79568697600, 1203310080000, 19381043404800, 331357630464000, 5993331073228800, 114354145640448000, 2295517848809472000, 48363337839624192000

Offset

0,4

Links

Harvey P. Dale, Table of n, a(n) for n = 0..449

Mathematica

Table[n!(1/Binomial[n, 0]-Sum[1/Binomial[n, d], {d, Floor[n/2]}]), {n, 0, 30}] (* Harvey P. Dale, Feb 03 2024 *)

Prog

(PARI) a(n) = n!*(1 - sum(k=1, floor(n/2), 1/binomial(n, k))); \\ Michel Marcus, Jul 10 2019

Crossrefs

Cf. A024420.

Sequence in context: A222497 A327355 A356508 * A259353 A339193 A352289

Adjacent sequences: A024418 A024419 A024420 * A024422 A024423 A024424

Keyword

nonn

Author

Clark Kimberling

Extensions

More terms from Sean A. Irvine, Jul 10 2019

Status

approved