Numbers N such that concatenation of N, N, and x generates a prime for x=1 and x=3 and x=7 and x=9.

Terms

a(0) =1235a(1) =4061a(2) =8255a(3) =22775a(4) =24665a(5) =36500a(6) =44501a(7) =52343a(8) =54434a(9) =57644a(10) =58109a(11) =59567a(12) =59588a(13) =65018a(14) =69407a(15) =71789a(16) =78689a(17) =94280a(18) =98594a(19) =106748a(20) =114272a(21) =122504a(22) =134369a(23) =137129a(24) =138905a(25) =144302a(26) =162236a(27) =196439a(28) =235808a(29) =238235