Boustrophedon transform of triangular numbers.

Terms

a(0) =1a(1) =4a(2) =13a(3) =39a(4) =120a(5) =407a(6) =1578a(7) =7042a(8) =35840a(9) =205253a(10) =1306454a(11) =9148392a(12) =69887664a(13) =578392583a(14) =5155022894a(15) =49226836114a(16) =501420422112