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A062779
a(n) = 2*n*(2*n)!.
1
0, 4, 96, 4320, 322560, 36288000, 5748019200, 1220496076800, 334764638208000, 115242726703104000, 48658040163532800000, 24728016011107368960000, 14890761641597746544640000, 10485577989291746525184000000
OFFSET
0,2
FORMULA
From Amiram Eldar, Feb 14 2021: (Start)
a(n) = A001563(2*n) = 2*n*A010050(n).
Sum_{n>=1} 1/a(n) = Chi(1) - gamma = A099284 - A001620, where Chi(x) is the hyperbolic cosine integral
Sum_{n>=1} (-1)^(n+1)/a(n) = gamma - Ci(1) = A001620 - A099282, where Ci(x) is the cosine integral. (End)
MATHEMATICA
a[n_] := 2*n*(2*n)!; Array[a, 14, 0] (* Amiram Eldar, Feb 14 2021 *)
PROG
(PARI) for(n=0, 22, print((2*n)*(2*n)!))
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Jason Earls, Jul 18 2001
STATUS
approved