A068989 - OEIS

A068989

Squares which when reversed are primes (ignore leading zeros).

16, 196, 361, 784, 1024, 1369, 1444, 1600, 1681, 3844, 7225, 7921, 9025, 9409, 11236, 14161, 18496, 19321, 19600, 36100, 37249, 38416, 70756, 73441, 75076, 76729, 78400, 78961, 97969, 99856, 102400, 105625, 107584, 109561, 111556, 112225

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OFFSET

1,1

LINKS

T. D. Noe, Table of n, a(n) for n=1..1000

EXAMPLE

40^2 = 1600. Reversing the digits we get 0061, which is the prime 61 padded with leading zeroes. Hence 1600 is in the sequence.

41^2 = 1681. Reversing the digits we get 1861, which is a prime. Hence 1681 is in the sequence.

42^2 = 1764. Reversing the digits we get 4671 = 3^3 * 173. So 1764 is not in the sequence.

MATHEMATICA

Do[s = i^2; If[PrimeQ[FromDigits[Reverse[IntegerDigits[s]]]], Print[s]], {i, 1, 10^2}] (* Pe *)

Select[Range[100]^2, PrimeQ[FromDigits[Reverse[IntegerDigits[#]]]] &] (* Alonso del Arte, Jan 07 2018 *)

PROG

(PARI) isok(n) = issquare(n) && isprime(fromdigits(Vecrev(digits(n)))); \\ Michel Marcus, Jan 07 2018

CROSSREFS

Cf. primes whose reversal is a square, A007488; numbers n such that n^2 reversed is a prime, A059007.

Sequence in context: A016280 A281946 A077363 * A017318 A173668 A373108

Adjacent sequences: A068986 A068987 A068988 * A068990 A068991 A068992

KEYWORD

easy,nonn,base

AUTHOR

Joseph L. Pe, Mar 12 2002

EXTENSIONS

More terms from Zak Seidov, Jan 26 2005

Edited by N. J. A. Sloane, Dec 23 2007

STATUS

approved