OFFSET
0,2
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..500
FORMULA
a(n) = -Sum_{i=0..n} binomial(n+i-2,n-2)*binomial(n+i-1,n-i))/(n-1), n>1; a(0)=1, a(1) = -2. - Vladimir Kruchinin, Feb 15 2013
PROG
(PARI) a(n) = if (n==0, 1, if (n==1, -2, -sum(i=0, n, binomial(n+i-2, n-2)*binomial(n+i-1, n-i))/(n-1))); \\ Michel Marcus, Dec 29 2018
CROSSREFS
KEYWORD
sign
AUTHOR
STATUS
approved