G.f.: exp( Sum_{n>=1} x^n / (n*(1-x)^n * (1-x^n)) ).

Terms

a(0) =1a(1) =1a(2) =3a(3) =7a(4) =16a(5) =35a(6) =76a(7) =162a(8) =342a(9) =715a(10) =1484a(11) =3060a(12) =6278a(13) =12824a(14) =26102a(15) =52969a(16) =107224a(17) =216601a(18) =436798a(19) =879584a(20) =1769117a(21) =3554726a(22) =7136736a(23) =14318524a(24) =28711315a(25) =57544864a(26) =115290624a(27) =230910993a(28) =462362571a(29) =925610398