Composite and every divisor (except 1) contains the digit 7.

Terms

a(0) =497a(1) =679a(2) =749a(3) =799a(4) =1207a(5) =1379a(6) =1739a(7) =1799a(8) =1897a(9) =2479a(10) =2627a(11) =2701a(12) =2779a(13) =3337a(14) =3713a(15) =3997a(16) =4607a(17) =4709a(18) =4711a(19) =4739a(20) =4757a(21) =4907a(22) =5173a(23) =5257a(24) =5327a(25) =5579a(26) =5729a(27) =5767a(28) =5789a(29) =6179