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%I #8 Dec 28 2023 19:39:43
%S 1,3,21,96,684,4320,35640,293760,2881440,29695680,345643200,
%T 4296499200,58518028800,851751936000,13338801100800,222145265664000,
%U 3934764739584000,73675580977152000,1455693852146688000,30238671742304256000,659012259039805440000
%N Second column (m=2) of triangle A144881 (S1hat(3)).
%F a(n) = A144881(n+2,2), n>=0.
%Y Cf. A144881, A001710 (first column), A144884 (third column).
%K nonn,easy
%O 0,2
%A _Wolfdieter Lang_, Oct 09 2008