a(1)=1, a(n)=a(n-1)+n^0 if n odd, a(n)=a(n-1)+ n^5 if n is even.

Terms

a(0) =1a(1) =33a(2) =34a(3) =1058a(4) =1059a(5) =8835a(6) =8836a(7) =41604a(8) =41605a(9) =141605a(10) =141606a(11) =390438a(12) =390439a(13) =928263a(14) =928264a(15) =1976840a(16) =1976841a(17) =3866409a(18) =3866410a(19) =7066410a(20) =7066411a(21) =12220043a(22) =12220044a(23) =20182668a(24) =20182669a(25) =32064045a(26) =32064046