The (7^n)-th composite number.

Terms

a(0) =4a(1) =14a(2) =69a(3) =426a(4) =2811a(5) =18964a(6) =129796a(7) =894425a(8) =6189788a(9) =42955634a(10) =298658894a(11) =2079246204a(12) =14489671674a(13) =101048453166a(14) =705093892472