a(1) = 1; a(n > 1) = Sum_{0 < k < n} (-1)^(n - k - 1) a(n - k) Sum_{d|k} a(d).

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =2a(5) =2a(6) =5a(7) =6a(8) =11a(9) =14a(10) =23a(11) =26a(12) =51a(13) =70a(14) =114a(15) =147a(16) =237a(17) =314a(18) =516a(19) =715a(20) =1118a(21) =1549a(22) =2353a(23) =3252a(24) =5011a(25) =7235a(26) =10724a(27) =15142a(28) =22504a(29) =32506