A227090 - OEIS

A227090

Numbers n such that n^2+1 with its digits reversed is prime (ignoring leading zeros).

%I #14 Jul 12 2013 03:06:14

%S 1,2,4,6,7,10,12,13,18,19,27,28,30,31,35,38,39,40,41,55,57,59,60,61,

%T 62,84,86,87,88,89,96,97,99,101,103,105,108,112,116,117,119,124,131,

%U 136,138,139,140,175,177,178,179,181,183,184,190,191,193,194,196,199,265,266,268,272,273,276,277,279,280,281,300,304,305

%N Numbers n such that n^2+1 with its digits reversed is prime (ignoring leading zeros).

%H K. D. Bajpai, <a href="/A227090/b227090.txt">Table of n, a(n) for n = 1..1200</a>

%e a(3)=4: 4^2+1=17. Reversing the digits gives 71 which is prime.

%p with(StringTools):K:= proc()local i,a,b,c;c:=1;for i from 1 to 10000 do;a:=parse(Reverse(convert((i^2+1),string))); b:=isprime(a);if b then lprint(c,i);c:=c+1;fi; od;end:K(); # _K. D. Bajpai_, Jun 30 2013

%p with(StringTools):K := proc(n) local i,a; a:=parse(Reverse(convert((n^2+1),string))):

%p if (isprime(a)) then RETURN (n) fi: end: seq(K(n), n=1..1500); # _K. D. Bajpai_, Jun 30 2013

%Y Cf. A002522, A004086.

%K nonn,base

%O 1,2

%A _K. D. Bajpai_, Jun 30 2013