OFFSET
1,1
COMMENTS
Number of terms less than 10^k: 0, 0, 1, 4, 13, 26, 74, 213, 615, 1773, 5000, 14356, 41474, 120186, 352310, 1035235, ... - Muniru A Asiru, Jan 19 2018 and David A. Corneth, Jan 12 2019
REFERENCES
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
Charles W. Trigg, Primes with Reverses That Are Powers, J. Rec. Math., 17 (1985), 172-176.
LINKS
David A. Corneth, Table of n, a(n) for n = 1..14356 (terms 1..1000 from T. D. Noe, terms 1001..1773 from Marius A. Burtea)
EXAMPLE
61 is in the sequence because 16 = 4^2.
163 is in the sequence because 361 = 19^2.
167 is not in the sequence because 761 is also prime, not a square.
MAPLE
revdigs:= proc(n)
local L, nL, j;
L:= convert(n, base, 10);
nL:= nops(L);
add(L[i]*10^(nL-i), i=1..nL);
end:
map(proc(i) local r; r:= revdigs(i^2); if isprime(r) then r else NULL fi end proc, {$1..9999}); # Robert Israel, Aug 14 2014
MATHEMATICA
Select[Prime[Range[16000]], IntegerQ[Sqrt[ToExpression[StringReverse[ToString[#]]]]] &]
Select[Prime[Range[16000]], IntegerQ[Sqrt[FromDigits[ Reverse[ IntegerDigits[ #]]]]] &] (* Harvey P. Dale, Jul 19 2011 *)
Select[Prime@ Range[10^5], IntegerQ@ Sqrt@ IntegerReverse@ # &] (* Michael De Vlieger, Jan 20 2018 *)
PROG
(Python)
from gmpy2 import is_square
from sympy import prime
A007488 = [prime(n) for n in range(1, 10**6) if is_square(int(str(prime(n))[::-1]))] # Chai Wah Wu, Aug 14 2014
(PARI) is(n)=isprime(n) && issquare(fromdigits(Vecrev(digits(n)))) \\ Charles R Greathouse IV, Feb 06 2017
(PARI) uptoQdigits(n) = {my(res=List(), i2); for(i=4, sqrtint(10^n), i2 = i^2; if(i%10!=0 && gcd(10, i2 \ (10^logint(i2, 10))) == 1, c=fromdigits(Vecrev(digits(i2))); if(isprime(c), listput(res, c) ) ) ); listsort(res); res } \\ David A. Corneth, Jan 12 2019
(Magma) [p: p in PrimesUpTo(150000)|IsSquare(Seqint(Reverse(Intseq(p))))]; // Marius A. Burtea, Jan 12 2019
CROSSREFS
KEYWORD
base,nonn,nice
AUTHOR
STATUS
approved