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 A007488 Primes whose reversal is a square. (Formerly M5321) 28
 61, 163, 487, 691, 1297, 1861, 4201, 4441, 4483, 5209, 5227, 9049, 9631, 12391, 14437, 16141, 16987, 61483, 63211, 65707, 65899, 67057, 69481, 92767, 94273, 96979, 106303, 108061, 123031, 123373, 125329, 127291, 129643, 142771, 146857, 148249, 165901 (list; graph; refs; listen; history; text; internal format)
 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 (first 1000 terms from T. D. Noe, next 773 terms by 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 Cf. A059007, A068989. See A132388 for another version. For prime reversals that are cubes, 4th powers, 5th powers, see A057699, A058996, A059000. - R. J. Mathar, Nov 13 2007 Sequence in context: A161853 A106096 A142482 * A142538 A057216 A139993 Adjacent sequences:  A007485 A007486 A007487 * A007489 A007490 A007491 KEYWORD base,nonn,nice AUTHOR STATUS approved

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Last modified December 2 18:14 EST 2020. Contains 338889 sequences. (Running on oeis4.)