a(n) = n(F(n+2) - 1) where F(n) is defined by A000045.

Terms

a(0) =0a(1) =1a(2) =4a(3) =12a(4) =28a(5) =60a(6) =120a(7) =231a(8) =432a(9) =792a(10) =1430a(11) =2552a(12) =4512a(13) =7917a(14) =13804a(15) =23940a(16) =41328a(17) =71060a(18) =121752a(19) =207955a(20) =354200a(21) =601776a(22) =1020074a(23) =1725552a(24) =2913408a(25) =4910425a(26) =8263060a(27) =13884156a(28) =23297092a(29) =39041772