Coefficient of x^n in (1+x+x^2+x^3+x^4)^n.

Terms

a(0) =1a(1) =1a(2) =3a(3) =10a(4) =35a(5) =121a(6) =426a(7) =1520a(8) =5475a(9) =19855a(10) =72403a(11) =265233a(12) =975338a(13) =3598180a(14) =13311000a(15) =49360405a(16) =183424355a(17) =682870587a(18) =2546441085a(19) =9509714340a(20) =35561166195a(21) =133138728845a(22) =499005557515