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 A045856 #21 Apr 15 2024 20:35:35 %S A045856 5,15,16,17,45,46,47,48,49,50,51,52,53,54,142,143,144,145,146,147,148, %T A045856 149,150,151,152,153,154,155,156,157,158,159,160,161,162,163,164,165, %U A045856 166,167,168,169,170,171,172,173,448,449,450,451,452,453,454,455,456 %N A045856 Numbers whose square has initial digit '2'. %H A045856 Seiichi Manyama, <a href="/A045856/b045856.txt">Table of n, a(n) for n = 1..10000</a> %t A045856 Select[Range[500],IntegerDigits[#^2][[1]]==2&] (* _Harvey P. Dale_, Apr 15 2024 *) %o A045856 (PARI) isok(n) = digits(n^2)[1] == 2; \\ _Michel Marcus_, May 28 2017 %Y A045856 Cf. A045785 %K A045856 nonn,base %O A045856 1,1 %A A045856 _Jeff Burch_ %E A045856 Corrected by _Seiichi Manyama_, May 28 2017