128*n^7-192*n^5+80*n^3-8*n.

Terms

a(0) =0a(1) =8a(2) =10864a(3) =235416a(4) =1905632a(5) =9409960a(6) =34356048a(7) =102213944a(8) =262184896a(9) =600940872a(10) =1260879920a(11) =2463542488a(12) =4538833824a(13) =7960697576a(14) =13389885712a(15) =21724469880a(16) =34158739328a(17) =52251130504a(18) =78001833456a(19) =113940720152a(20) =163226239840a(21) =229755926568a(22) =318289163984a(23) =434582852536