Primes that contain digits 1 and 4 only.

Terms

a(0) =11a(1) =41a(2) =4111a(3) =4441a(4) =11411a(5) =14411a(6) =41141a(7) =41411a(8) =44111a(9) =1114111a(10) =1144141a(11) =1144441a(12) =1411141a(13) =1411411a(14) =1441411a(15) =1444111a(16) =1444411a(17) =1444441a(18) =4141441a(19) =4414411a(20) =4441111a(21) =4441441a(22) =11111141a(23) =11141111a(24) =11141441a(25) =11441141a(26) =11441411a(27) =14111441a(28) =14141411