login
A136631
Antidiagonal sums of triangle A136630, omitting antidiagonals of all zeros.
1
1, 1, 2, 6, 28, 177, 1449, 14869, 185230, 2738962, 47287352, 939759621, 21241309681, 540698975061, 15370957337418, 484433735633218, 16817886069720724, 639545680226171989, 26507567678760284105
OFFSET
0,3
FORMULA
a(n) = Sum_{k=0..n} [x^(2n-2k)] Product_{j=0..[k/2]} 1/(1 - (2j + k-2[k/2])^2*x^2).
PROG
(PARI) {a(n)=sum(k=0, n, polcoeff(1/prod(j=0, k\2, 1-(2*j+(k%2))^2*x^2 +x*O(x^(2*n-2*k))), 2*n-2*k))}
CROSSREFS
Cf. A136630, A003724 (row sums of A136630).
Sequence in context: A088501 A140092 A052809 * A002435 A276911 A104018
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Jan 14 2008
STATUS
approved