This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A175823 #12 May 24 2025 02:46:37 %S A175823 1,9,297,513,783,999,1323,1331,4961,10989,11979,12969,14733,20402, %T A175823 29088,89109,99999,109989,122221,188887,210789,218097,377199,477773, %U A175823 483516,525503,718189,1099989,2128806,2920819,7769223,9999999,10999989,12222221,19097181,21510896 %N A175823 Numbers k such that gcd(k^2, reverse(k^2)) = k. %e A175823 297 is in the sequence, because 297^2 = 88209, and reverse(88209) = 90288 = 297*304. %t A175823 Select[Range[5000000], GCD[FromDigits[Reverse[IntegerDigits[(#)^2 ]]],#^2]==# &] %o A175823 (PARI) isok(k) = gcd(k^2, fromdigits(Vecrev(digits(k^2)))) == k; \\ _Amiram Eldar_, May 24 2025 %Y A175823 Cf. A004086, A055483. %K A175823 nonn,base %O A175823 1,2 %A A175823 _Michel Lagneau_, Sep 13 2010 %E A175823 More terms from _Amiram Eldar_, May 24 2025