%I #31 Feb 20 2015 03:53:40

%S 0,1,2,3,4,7,17,24,59,199,743,2558,4896,5539,6192,10977,27679

%N Numbers n such that "n 42's followed by 43" is prime.

%C Equivalently, a(n) generates primes of the form (100^(1+a(n)) - 1) * 42/99 + 1. - _Mohsen Hozan_, Jan 23 2015

%t t = 1; Do[ t = t*100 - 57; If[PrimeQ[t], Print[n]], {n, 0, 3000}]

%t robinsonQ[n_] := PrimeQ[(100^(1 + n) - 1) * 42/99 + 1]; Select[Range[200], robinsonQ] (* _Robert G. Wilson v_, Jan 23 2015 *)

%o (PARI) t=1; for(n=0,10^6,t=100*t-57;if(ispseudoprime(t),print1(n,", "))); \\ _Joerg Arndt_, Nov 21 2014

%o (PFGW) ABC2 1+(100^(1+$a)-1)*42/99

%o a: from 0 to 28000 \\ _Charles R Greathouse IV_, _Mohsen Hozan_, Jan 23 2015

%Y Cf. A110704, A254002.

%K nonn,base,more

%O 1,3

%A _Ray Chandler_, Aug 04 2005

%E a(13)-a(17) from _Mohsen Hozan_, Feb 10 2015