%I
%S 1,5,19,22,26,29,32,35,37,38,44,46,52,56,59,61,65,67,68,70,71,77,82,
%T 86,89,94,95,109,112,116,133,137,140,146,151,155,160,172,181,187,190,
%U 194,197,203,209,211,212,218,221,229,245,253,254,263,265,281,286,292
%N Numbers k such that k prefixed by '6' and followed by '9' is a prime.
%t Select[Range@300,PrimeQ@FromDigits@Flatten[{6,IntegerDigits@#,9}]&] (* _Giorgos Kalogeropoulos_, Jul 28 2021 *)
%o (Python)
%o from sympy import isprime
%o def ok(n): return isprime(int('6'+str(n)+'9'))
%o print(list(filter(ok, range(293)))) # _Michael S. Branicky_, Jul 28 2021
%Y Subsequence of A001651 (not divisible by 3).
%K nonn,base
%O 1,2
%A _Patrick De Geest_, May 15 1998
