a(n) = n^4 - 15*n + 15.

Terms

a(0) =1a(1) =1a(2) =51a(3) =211a(4) =565a(5) =1221a(6) =2311a(7) =3991a(8) =6441a(9) =9865a(10) =14491a(11) =20571a(12) =28381a(13) =38221a(14) =50415a(15) =65311a(16) =83281a(17) =104721a(18) =130051a(19) =159715a(20) =194181a(21) =233941a(22) =279511a(23) =331431a(24) =390265a(25) =456601a(26) =531051a(27) =614251a(28) =706861a(29) =809565