Numbers k such that concat(k, d(k)) and concat(d(k), k) are both prime, where d(k) is the number of divisors of k.

A284643

Numbers k such that concat(k, d(k)) and concat(d(k), k) are both prime, where d(k) is the number of divisors of k.

Terms

    a(0) =1a(1) =121a(2) =169a(3) =361a(4) =1849a(5) =14161a(6) =17689a(7) =25921a(8) =41209a(9) =51529a(10) =52441a(11) =64009a(12) =69169a(13) =76729a(14) =124609a(15) =187489a(16) =247009a(17) =436921a(18) =776161a(19) =851929a(20) =935089a(21) =1207801a(22) =1951609a(23) =2582449a(24) =3179089a(25) =3829849a(26) =4363921a(27) =4481689a(28) =5094049a(29) =6911641

External references