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A167217 Primes such that their reversal + 1 is a square. 3

%I

%S 3,53,827,3671,5507,8423,8693,30293,42083,42281,42299,53639,57203,

%T 59921,80819,326681,345473,345887,348191,361637,387449,420803,422243,

%U 510299,511019,551339,574181,590813,593171,804653,806363,808991,829601,863729,867131,888011

%N Primes such that their reversal + 1 is a square.

%H Robert Israel and K. D. Bajpai, <a href="/A167217/b167217.txt">Table of n, a(n) for n = 1..10000</a> (first 506 entries from Bajpai)

%e 53 is prime and 35 + 1 = 36 = 6^2.

%e 827 is in the sequence because it is prime. Also, reversal(827) + 1 = 728 + 1 = 729 = 27^2. - _K. D. Bajpai_, Jul 03 2014

%p Nd:= 4: # to get all entries with up to 2*Nd digits

%p revdigs:= proc(x) local F,n,i;

%p F:= convert(x,base,10);

%p n:= nops(F);

%p add(10^(n-i)*F[i],i=1..n);

%p end:

%p Sq:= remove(t -> (t mod 10 = 1), {seq(i^2,i=1..10^Nd-1)}):

%p A:=map(proc(s) local r; r:= revdigs(s-1); if isprime(r) then r else NULL fi end proc, Sq); # _Robert Israel_, Jul 03 2014

%t Select[Prime[Range[10^5]], IntegerQ[Sqrt[FromDigits[Reverse[IntegerDigits[#]]] + 1]] &] (* _K. D. Bajpai_, Jul 03 2014 *)

%K base,nonn

%O 1,1

%A _Claudio Meller_, Oct 30 2009

%E More terms from _K. D. Bajpai_, Jul 03 2014

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Last modified September 23 20:42 EDT 2021. Contains 347617 sequences. (Running on oeis4.)