A167217 Primes whose reversal + 1 is a square.

3, 53, 827, 3671, 5507, 8423, 8693, 30293, 42083, 42281, 42299, 53639, 57203, 59921, 80819, 326681, 345473, 345887, 348191, 361637, 387449, 420803, 422243, 510299, 511019, 551339, 574181, 590813, 593171, 804653, 806363, 808991, 829601, 863729, 867131, 888011

Offset

1,1

Links

Robert Israel and K. D. Bajpai, Table of n, a(n) for n = 1..10000 (first 506 entries from K. D. Bajpai)

Example

53 is prime and 35 + 1 = 36 = 6^2.
827 is in the sequence because it is prime and reversal(827) + 1 = 728 + 1 = 729 = 27^2. - K. D. Bajpai, Jul 03 2014

Maple

Nd:= 4: # to get all entries with up to 2*Nd digits
revdigs:= proc(x) local F, n, i;
F:= convert(x, base, 10);
n:= nops(F);
add(10^(n-i)*F[i], i=1..n);
end:
Sq:= remove(t -> (t mod 10 = 1), {seq(i^2, i=1..10^Nd-1)}):
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

Mathematica

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

Crossrefs

Sequence in context: A173802 A001279 A092447 * A203561 A333563 A273802

Adjacent sequences: A167214 A167215 A167216 * A167218 A167219 A167220

Keyword

base,nonn

Author

Claudio Meller, Oct 30 2009

Extensions

More terms from K. D. Bajpai, Jul 03 2014

Status

approved