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 A080162 #19 Jun 16 2025 19:52:00
%S A080162 1,121,12321,1234321,123454321,12345654321,1234567654321,
%T A080162 123456787654321,12345678987654321,
%U A080162 12345679012345679012345679012345678987654320987654320987654320987654321
%N A080162 Wonderful Demlo numbers A002477 whose digit sums are squares.
%C A080162 The next term (a(11)) has 101 digits. - _Harvey P. Dale_, Jun 16 2025
%H A080162 Jeppe Stig Nielsen, <a href="/A080162/b080162.txt">Table of n, a(n) for n = 1..23</a>
%H A080162 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/DemloNumber.html">Demlo Number</a>
%t A080162 Select[LinearRecurrence[{111,-1110,1000},{1,121,12321},40],IntegerQ[Sqrt[Total[IntegerDigits[#]]]]&] (* _Harvey P. Dale_, Jun 16 2025 *)
%o A080162 (PARI) for(k=1,100,my(d=((10^k-1)/9)^2); issquare(sumdigits(d)) && print1(d,", ")) \\ _Jeppe Stig Nielsen_, May 27 2023
%Y A080162 Cf. A080160, A080161, A002477, A080151.
%K A080162 nonn,base
%O A080162 1,2
%A A080162 _Eric W. Weisstein_, Jan 31 2003