1 - (5/6)*n + (5/2)*n^2 + (10/3)*n^3 + n^4.

Terms

a(0) =1a(1) =7a(2) =52a(3) =192a(4) =507a(5) =1101a(6) =2102a(7) =3662a(8) =5957a(9) =9187a(10) =13576a(11) =19372a(12) =26847a(13) =36297a(14) =48042a(15) =62426a(16) =79817a(17) =100607a(18) =125212a(19) =154072a(20) =187651a(21) =226437a(22) =270942a(23) =321702a(24) =379277a(25) =444251a(26) =517232a(27) =598852a(28) =689767a(29) =790657