A090270 - OEIS

A090270

Least positive r such that concatenation k, r, k is prime, where k == 1,3,7 or 9 (mod 10) in increasing order.

%I #5 Dec 05 2013 19:56:37

%S 3,1,2,1,3,3,1,2,1,6,1,1,2,5,3,1,1,5,1,5,1,3,4,1,2,4,5,22,1,6,3,2,1,3,

%T 1,1,2,4,3,14,12,15,4,3,4,1,1,1,2,14,3,4,1,3,1,8,1,4,5,6,3,4,14,1,1,5,

%U 3,3,2,6,1,3,26,2,6,1,7,2,3,21,1,3,2,6,3,2,9,10,4,3,15,9,4,7,5,1,3,5,5,5,16

%N Least positive r such that concatenation k, r, k is prime, where k == 1,3,7 or 9 (mod 10) in increasing order.

%e 131,313,727,919,11311,... etc. are primes.

%Y Cf. A090271.

%K base,nonn

%O 1,1

%A _Amarnath Murthy_, Nov 28 2003

%E More terms from _Joshua Zucker_, May 03 2006