a(n) is the smallest k such that (k^4 + 1)/(n^4 + 1) is an integer > 1.

Terms

a(0) =3a(1) =8a(2) =27a(3) =64a(4) =125a(5) =216a(6) =343a(7) =474a(8) =43a(9) =781a(10) =1331a(11) =1728a(12) =2197a(13) =1807a(14) =3375a(15) =4096a(16) =4913a(17) =1600a(18) =807a(19) =8000a(20) =9261a(21) =10648a(22) =12167a(23) =13824a(24) =7353a(25) =17576a(26) =6721a(27) =21952a(28) =24389a(29) =27000