a(0) = 0. If n is odd, a(n) = a(n-1) + n, otherwise a(n) = a(n-1) * n.

Terms

a(0) =0a(1) =1a(2) =2a(3) =5a(4) =20a(5) =25a(6) =150a(7) =157a(8) =1256a(9) =1265a(10) =12650a(11) =12661a(12) =151932a(13) =151945a(14) =2127230a(15) =2127245a(16) =34035920a(17) =34035937a(18) =612646866a(19) =612646885a(20) =12252937700a(21) =12252937721a(22) =269564629862a(23) =269564629885