a(n) = n^4 if n odd, 7*n^4/8 if n even.

Terms

a(0) =0a(1) =1a(2) =14a(3) =81a(4) =224a(5) =625a(6) =1134a(7) =2401a(8) =3584a(9) =6561a(10) =8750a(11) =14641a(12) =18144a(13) =28561a(14) =33614a(15) =50625a(16) =57344a(17) =83521a(18) =91854a(19) =130321a(20) =140000a(21) =194481a(22) =204974a(23) =279841a(24) =290304a(25) =390625a(26) =399854a(27) =531441a(28) =537824a(29) =707281