A368894 a(n) = Sum_{k=0..floor(n/2)} (-n)^k * binomial(n-k,k).
1, 1, -1, -5, 5, 56, -29, -923, -119, 19855, 17711, -524160, -926771, 16339441, 45275035, -585443909, -2298643951, 23626165600, 124604211943, -1056587815835, -7261611779179, 51645640102519, 455056929514067, -2724884512463520, -30595315890959975
Offset: 0
Programs
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PARI
a(n) = sum(k=0, n\2, (-n)^k*binomial(n-k, k));
Formula
a(n) = [x^n] 1/(1 - x + n*x^2).