a(1)=1, a(n) = a(n-1) + n^5 if n odd, a(n) = a(n-1) + n^3 if n is even.

Terms

a(0) =1a(1) =9a(2) =252a(3) =316a(4) =3441a(5) =3657a(6) =20464a(7) =20976a(8) =80025a(9) =81025a(10) =242076a(11) =243804a(12) =615097a(13) =617841a(14) =1377216a(15) =1381312a(16) =2801169a(17) =2807001a(18) =5283100a(19) =5291100a(20) =9375201a(21) =9385849a(22) =15822192a(23) =15836016a(24) =25601641a(25) =25619217a(26) =39968124a(27) =39990076a(28) =60501225