Coefficient of x^8 in expansion of (1+x+x^2)^n.

Terms

a(0) =1a(1) =15a(2) =90a(3) =357a(4) =1107a(5) =2907a(6) =6765a(7) =14355a(8) =28314a(9) =52624a(10) =93093a(11) =157950a(12) =258570a(13) =410346a(14) =633726a(15) =955434a(16) =1409895a(17) =2040885a(18) =2903428a(19) =4065963a(20) =5612805a(21) =7646925a(22) =10293075a(23) =13701285a(24) =18050760a(25) =23554206a(26) =30462615a(27) =39070540a(28) =49721892a(29) =62816292