A013604 3^n-prevprime(3^n), where prevprime(x) = largest prime < x.

1, 2, 4, 2, 2, 2, 8, 8, 2, 20, 16, 58, 22, 8, 16, 98, 10, 10, 14, 8, 4, 2, 20, 28, 20, 20, 26, 22, 14, 26, 4, 34, 52, 56, 28, 10, 2, 10, 58, 38, 2, 122, 74, 34, 22, 22, 46, 44, 50, 46, 16, 124, 4, 10, 106, 10, 26, 220, 38, 160, 74, 8, 28, 104, 104, 38, 298, 94, 16