A231756 - OEIS

%I #16 Dec 04 2018 20:50:40

%S 1,2,5,8,9,10,15,16,17,20,26,29,46,50,51,52,79,80,81,83,90,92,94,100,

%T 142,144,149,150,159,160,161,162,167,168,170,171,172,173,200,246,247,

%U 251,254,255,258,259,260,262,264,283,284,287,289,290,297,299,449,454

%N Numbers n such that reversal (n^2) plus 1 is prime.

%C If n is a multiple of 10, after reversal leading zeros are discarded before adding 1.

%H K. D. Bajpai, <a href="/A231756/b231756.txt">Table of n, a(n) for n = 1..5500</a>

%e a(3)= 5: 5^2= 25: reversing the digits gives 52: 52+1= 53 which is prime.

%e a(7)= 15: 15^2= 225: reversing the digits gives 522: 522+1= 523 which is prime.

%p with(StringTools):KD:= proc() local a; a:= parse(Reverse(convert((n^2), string)))+1;if isprime(a) then RETURN (n): fi;end: seq(KD(), n=1..1000);

%t Select[Range[500], PrimeQ[ToExpression[StringReverse[ToString[#^2]]] + 1] &]

%t Select[Range[500],PrimeQ[IntegerReverse[#^2]+1]&] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Dec 04 2018 *)

%Y Cf.  A005574 (numbers n: n^2 + 1 is prime).

%Y Cf. A059007 (numbers n: n^2 reversed is a prime).

%K nonn,base

%O 1,2

%A _K. D. Bajpai_, Nov 21 2013