Numbers n such that 1n1, 3n3, 7n7 and 9n9 are all primes.

Terms

a(0) =20a(1) =53a(2) =341a(3) =536a(4) =2312a(5) =2477a(6) =3380a(7) =3665a(8) =3686a(9) =4547a(10) =5009a(11) =5105a(12) =6458a(13) =6488a(14) =6731a(15) =6845a(16) =7499a(17) =7508a(18) =7562a(19) =7835a(20) =8411a(21) =8831a(22) =9032a(23) =9386a(24) =9764a(25) =9839a(26) =11027a(27) =11885a(28) =14990a(29) =19589