A175823 Numbers k such that gcd(k^2, reverse(k^2)) = k.

1, 9, 297, 513, 783, 999, 1323, 1331, 4961, 10989, 11979, 12969, 14733, 20402, 29088, 89109, 99999, 109989, 122221, 188887, 210789, 218097, 377199, 477773, 483516, 525503, 718189, 1099989, 2128806, 2920819, 7769223, 9999999, 10999989, 12222221, 19097181, 21510896

Offset: 1

Author

Michel Lagneau, Sep 13 2010

Keywords

• nonn
• base

Examples

			297 is in the sequence, because 297^2 = 88209, and reverse(88209) = 90288 = 297*304.
		

Crossrefs

Cf. A004086, A055483.

Programs

Mathematica

Select[Range[5000000], GCD[FromDigits[Reverse[IntegerDigits[(#)^2 ]]],#^2]==# &]

PARI

isok(k) = gcd(k^2, fromdigits(Vecrev(digits(k^2)))) == k; \\ Amiram Eldar, May 24 2025

Extensions

More terms from Amiram Eldar, May 24 2025