A363780 a(n) = [x^n] 1/(Sum_{k>=0} x^(k^2))^n.
1, -1, 3, -10, 31, -96, 294, -876, 2511, -6796, 16698, -33540, 31174, 184534, -1627812, 8912760, -41466433, 176963760, -714194382, 2766892840, -10374065814, 37815483948, -134334781732, 465432203640, -1571910265770, 5164302815179, -16438631981418
Offset: 0