G.f.: Product_{n>=1} [1 + (n+1)*x^n + (n+2)*x^(n+1) + (n+3)*x^(n+2) + (n+4)*x^(n+3) +...].

Terms

a(0) =1a(1) =2a(2) =6a(3) =18a(4) =45a(5) =108a(6) =252a(7) =578a(8) =1270a(9) =2716a(10) =5678a(11) =11678a(12) =23664a(13) =47182a(14) =92538a(15) =178892a(16) =341481a(17) =644648a(18) =1205062a(19) =2231304a(20) =4092646a(21) =7437680a(22) =13398520a(23) =23939558a(24) =42451586a(25) =74754652a(26) =130777182a(27) =227346498a(28) =392806891a(29) =674630766