OFFSET
0,2
COMMENTS
1-a(n+1) equals the n-th partial sum of the Genocchi numbers (A001469).
FORMULA
a(n) = 1 - Sum_{k=1, n} A001469(k) for n>0, with a(0)=1.
This sequence's twin numbers are given in A133135. - Paul Curtz, Aug 07 2008
PROG
(PARI) {a(n)=local(M=matrix(n+2, n+2)); M[1, 1]=1; if(n>0, M[2, 1]=1; M[2, 2]=1); for(r=3, n+2, for(c=1, r, M[r, c]=if(c==1, M[r-1, 1], if(c==r, 1, M[r, c]=M[r-1, c]-((matrix(r-1, r-1, i, j, M[i, j]))^-1)[r-1, c-1])))); return(if(n==0, 1, M[n+2, 2]))}
CROSSREFS
KEYWORD
sign
AUTHOR
Paul D. Hanna, Dec 28 2004
STATUS
approved