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Bisection of A003319: a(n) = A003319(2n+1).
3

%I #11 Aug 03 2022 17:46:31

%S 1,3,71,3447,273343,31998903,5201061455,1123596277863,311951144828863,

%T 108355864447215063,46066653228356851631,23539631662517304379719,

%U 14238556471214701698866335,10063612905845566536549621687,8219089293266835899526592972943,7682002790499533568011331441585447

%N Bisection of A003319: a(n) = A003319(2n+1).

%H Vincenzo Librandi, <a href="/A272657/b272657.txt">Table of n, a(n) for n = 0..200</a>

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

%Y Cf. A003319, A272656.

%K nonn

%O 0,2

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