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A024421
a(n) = n!*(1/C(n,0) - 1/C(n,1) - ... - 1/C(n,[ n/2 ])).
1
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
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
KEYWORD
nonn
EXTENSIONS
More terms from Sean A. Irvine, Jul 10 2019
STATUS
approved