a(n) = 1^n + 4^n + 6^n.

Terms

a(0) =3a(1) =11a(2) =53a(3) =281a(4) =1553a(5) =8801a(6) =50753a(7) =296321a(8) =1745153a(9) =10339841a(10) =61514753a(11) =366991361a(12) =2193559553a(13) =13127802881a(14) =78632599553a(15) =471258726401