Total number of triangles in all polyiamonds with n triangles.

Terms

a(0) =1a(1) =2a(2) =3a(3) =12a(4) =20a(5) =72a(6) =168a(7) =528a(8) =1440a(9) =4480a(10) =13046a(11) =40008a(12) =120055a(13) =366324a(14) =1109745a(15) =3380752a(16) =10269819a(17) =31253904a(18) =95011267a(19) =288979680a(20) =878550498a(21) =2671223720a(22) =8120041693a(23) =24682865208a(24) =75020015675a(25) =227999634772a(26) =692872971246