%I #17 Sep 05 2024 19:28:43
%S 2,10,14,20,28,38,40,50,52,58,62,64,70,80,82,100,104,110,112,118,122,
%T 124,142,148,160,164,170,172,178,188,194,208,218,224,230,238,244,248,
%U 250,260,262,274,284,292,298,308,320,338,344,352,362,364,382,398,400
%N Numbers k such that k concatenated with k+9 is a prime.
%H Robert Israel, <a href="/A032624/b032624.txt">Table of n, a(n) for n = 1..10000</a>
%p tcat:= (a,b) -> a*10^(1+ilog10(b))+b:
%p select(t -> isprime(tcat(t,t+9)), [seq(i,i=2..1000,2)]); # _Robert Israel_, Sep 04 2024
%t Select[Range[400],PrimeQ[FromDigits[Join[IntegerDigits[#],IntegerDigits[#+9]]]]&] (* _Stefano Spezia_, Sep 04 2023 *)
%Y Cf. A032614.
%K nonn,base
%O 1,1
%A _Patrick De Geest_, May 15 1998