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 A036523 #12 Mar 22 2020 17:31:05 %S A036523 6,66,666,66066,5666661,36666766,646686666,77666666626,4666660668676, %T A036523 66488766666666,6666063656661696,6666664664655666,666416695266666666, %U A036523 56666136666666763866,626646696666896766666,11666966196628666666666,66666666636866637006666,2626660686666666671166666 %N A036523 Smallest triangular number containing exactly n 6's. %t A036523 nsmall = Table[Infinity, 20]; %t A036523 For[i = 0, i <= 10^6, i++, p = PolygonalNumber[i]; %t A036523 n0 = Count[IntegerDigits[p], 6]; %t A036523 If[nsmall[[n0]] > p, nsmall[[n0]] = p]]; %t A036523 ReplaceAll[nsmall, Infinity -> "?"] (* _Robert Price_, Mar 22 2020 *) %Y A036523 Cf. A048361, A036517-A036526. %K A036523 nonn,base %O A036523 1,1 %A A036523 _David W. Wilson_ %E A036523 a(13)-a(18) from _Giovanni Resta_, Oct 30 2019