OFFSET
0,3
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..449
Eric Weisstein's World of Mathematics, Pochhammer Symbol.
FORMULA
a(n) = Sum_{k=0..floor(n/2)} 3^k * |Stirling1(n,2*k)|.
a(n) = ( (sqrt(3))_n + (-sqrt(3))_n )/2, where (x)_n is the Pochhammer symbol.
a(0) = 1, a(1) = 0; a(n) = (2*n-3) * a(n-1) - (n^2-4*n+1) * a(n-2).
PROG
(PARI) my(N=30, x='x+O('x^N)); apply(round, Vec(serlaplace(cosh(sqrt(3)*log(1-x)))))
(PARI) a(n) = sum(k=0, n\2, 3^k*abs(stirling(n, 2*k, 1)));
(PARI) a(n) = round((prod(k=0, n-1, sqrt(3)+k)+prod(k=0, n-1, -sqrt(3)+k)))/2;
(PARI) a_vector(n) = my(v=vector(n+1)); v[1]=1; v[2]=0; for(i=2, n, v[i+1]=(2*i-3)*v[i]-(i^2-4*i+1)*v[i-1]); v;
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Oct 10 2022
STATUS
approved