Expansion of Sum_{n>=1} ( (3 + x^n)^n - 3^n ).

Terms

a(0) =1a(1) =6a(2) =27a(3) =109a(4) =405a(5) =1467a(6) =5103a(7) =17550a(8) =59050a(9) =197100a(10) =649539a(11) =2126991a(12) =6908733a(13) =22325625a(14) =71744625a(15) =229602925a(16) =731794257a(17) =2324602206a(18) =7360989291a(19) =23245524600a(20) =73222475256a(21) =230128853031a(22) =721764371007