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

Terms

a(0) =1a(1) =3a(2) =246a(3) =250a(4) =3375a(5) =3381a(6) =20188a(7) =20196a(8) =79245a(9) =79255a(10) =240306a(11) =240318a(12) =611611a(13) =611625a(14) =1371000a(15) =1371016a(16) =2790873a(17) =2790891a(18) =5266990a(19) =5267010a(20) =9351111a(21) =9351133a(22) =15787476a(23) =15787500a(24) =25553125a(25) =25553151a(26) =39902058a(27) =39902086a(28) =60413235