a(1)=1, a(n)=a(n-1)+n^2 if n odd, a(n)=a(n-1)+ n^5 if n is even.

Terms

a(0) =1a(1) =33a(2) =42a(3) =1066a(4) =1091a(5) =8867a(6) =8916a(7) =41684a(8) =41765a(9) =141765a(10) =141886a(11) =390718a(12) =390887a(13) =928711a(14) =928936a(15) =1977512a(16) =1977801a(17) =3867369a(18) =3867730a(19) =7067730a(20) =7068171a(21) =12221803a(22) =12222332a(23) =20184956a(24) =20185581a(25) =32066957a(26) =32067686a(27) =49278054a(28) =49278895