Composite integers k such that gcd(phi(k), k - 1) > 1.

Terms

a(0) =9a(1) =15a(2) =21a(3) =25a(4) =27a(5) =28a(6) =33a(7) =35a(8) =39a(9) =45a(10) =49a(11) =51a(12) =52a(13) =55a(14) =57a(15) =63a(16) =65a(17) =66a(18) =69a(19) =70a(20) =75a(21) =76a(22) =77a(23) =81a(24) =85a(25) =87a(26) =91a(27) =93a(28) =95a(29) =99