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%I #6 Sep 21 2015 17:23:55
%S 1,7,136,5832,407808,47882880,5893585920,2763273139200,
%T -1770980740300800,6081299047511654400,-24479310471391641600000,
%U 147692341217380307927040000,-1254349086918655739874508800000,14641717268146696857494972006400000,-229475387530005564381034470860390400000
%N a(n) = (2*n+1)!*Sum_{k=0..n} B(2*k), B(n) the n-th Bernoulli number.
%C It appears that for n > 6, a(n)*(-1)^n < 0. (This comment was inspired by an observation of Robert Israel in A061053.)
%p a := n -> (2*n+1)!*add(bernoulli(2*k), k=0..n): seq(a(n), n=0..30);
%t Table[(2 n + 1)! Sum[BernoulliB[2 k], {k, 0, n}], {n, 0, 14}] (* _Michael De Vlieger_, Sep 21 2015 *)
%Y Cf. A061053.
%K sign
%O 0,2
%A _Peter Luschny_, Sep 21 2015
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