64*n^7 - 112*n^5 + 56*n^3 - 7*n.

Terms

a(0) =0a(1) =1a(2) =5042a(3) =114243a(4) =937444a(5) =4656965a(6) =17057046a(7) =50843527a(8) =130576328a(9) =299537289a(10) =628855930a(11) =1229215691a(12) =2265463212a(13) =3974443213a(14) =6686381534a(15) =10850138895a(16) =17062657936a(17) =26102926097a(18) =38970776898a(19) =56930852179a(20) =81562047860a(21) =114812765781a(22) =159062294182