a(n) = 1^n + 2^n + 5^n.

Terms

a(0) =3a(1) =8a(2) =30a(3) =134a(4) =642a(5) =3158a(6) =15690a(7) =78254a(8) =390882a(9) =1953638a(10) =9766650a(11) =48830174a(12) =244144722a(13) =1220711318a(14) =6103532010a(15) =30517610894a(16) =152587956162a(17) =762939584198