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 A290449 #16 Jan 02 2025 12:47:31 %S A290449 9,45,55,99,703,999,4950,5050,7272,7777,9999,77778,82656,95121,99999, %T A290449 318682,329967,351352,356643,390313,461539,466830,499500,500500, %U A290449 533170,538461,609687,643357,648648,670033,681318,791505,812890,818181,851851,857143,961038 %N A290449 Square roots of terms in A238237. %C A290449 Yet another variant of the Kaprekar numbers A006886. %H A290449 Rémy Sigrist, <a href="/A290449/b290449.txt">Table of n, a(n) for n = 1..25000</a> %t A290449 Sqrt[Select[Range[600000]^2, EvenQ[len=IntegerLength[#]] && # == (Mod[#, 10^(len/2)] + Floor[#/10^(len/2)])^2 &]] (* _Stefano Spezia_, Jan 01 2025 *) %Y A290449 Cf. A238237, A006886. %K A290449 nonn,base %O A290449 1,1 %A A290449 _N. J. A. Sloane_, Aug 06 2017, following a suggestion from _Max Alekseyev_