Expansion of Product_{k>=0} ((1+x^(3*k+1))/(1-x^(3*k+1)))^3.

Terms

a(0) =1a(1) =6a(2) =18a(3) =38a(4) =72a(5) =138a(6) =254a(7) =432a(8) =708a(9) =1154a(10) =1836a(11) =2826a(12) =4288a(13) =6456a(14) =9552a(15) =13902a(16) =20070a(17) =28722a(18) =40614a(19) =56916a(20) =79242a(21) =109448a(22) =149988a(23) =204318a(24) =276672a(25) =372288a(26) =498264a(27) =663602a(28) =879252a(29) =1159470