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Bisection of A003319: a(n) = A003319(2n).
3

%I #18 Aug 03 2022 17:46:54

%S 1,1,13,461,29093,2829325,392743957,73943424413,18176728317413,

%T 5661698774848621,2181096921557783605,1018705098450570562877,

%U 567347013156626397484421,371514945708955154128328461,282629242654284555347577144277,247210800978211588125067686948317

%N Bisection of A003319: a(n) = A003319(2n).

%H Michael De Vlieger, <a href="/A272656/b272656.txt">Table of n, a(n) for n = 0..224</a> (a(n) for n = 1..200 from Vincenzo Librandi)

%t (* b = A003319 *) b[n_] := b[n] = n! - Sum[k!*b[n-k], {k, 1, n-1} ]; a[n_] := b[2 n]; Table[a[n], {n, 0, 15}] (* _Jean-François Alcover_, Feb 18 2018 *)

%Y Cf. A003319, A272657.

%K nonn

%O 0,3

%A _N. J. A. Sloane_, May 15 2016

%E a(0) = 1 set by _Peter Luschny_, Aug 03 2022