Is A093468 a(1) = 1, a(2) = 2; for n >= 2, a(n+1) = a(n) + Sum {a(n)-a(i), i = 1 to n}. identical to Partial sums of A001710 Order of alternating group A_n, or number of even permutations of n letters. Both begin: 1, 2, 3, 6, 18, 78, 438, 2958, 23118, ... Thanks, Jonathan Vos Post