a(1) = 1, a(2) = 2, a(n+1) = n*a(1) + (n-1)*a(2) + ... + (n-r)*a(r+1) + ... + a(n).

Terms

a(0) =1a(1) =2a(2) =4a(3) =11a(4) =29a(5) =76a(6) =199a(7) =521a(8) =1364a(9) =3571a(10) =9349a(11) =24476a(12) =64079a(13) =167761a(14) =439204a(15) =1149851a(16) =3010349a(17) =7881196a(18) =20633239a(19) =54018521a(20) =141422324a(21) =370248451a(22) =969323029a(23) =2537720636a(24) =6643838879a(25) =17393796001a(26) =45537549124a(27) =119218851371a(28) =312119004989a(29) =817138163596