A068039 Number of subsets of {1,2,3,...,n} that sum to 0 mod 18.

1, 1, 1, 1, 1, 1, 3, 8, 16, 30, 58, 115, 229, 456, 912, 1824, 3643, 7286, 14572, 29132, 58262, 116522, 233024, 466048, 932096, 1864150, 3728300, 7456600, 14913112, 29826220, 59652436, 119304704, 238609408, 477218816, 954437292, 1908874584