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 A353144 #12 Apr 27 2022 19:48:37 %S A353144 0,1,21,421,13421,323421,12023421,241023421,10321023421,211421023421, %T A353144 4233421023421,140223421023421,3310023421023421,121201023421023421, %U A353144 2424021023421023421,104030421023421023421,2131113421023421023421,43122323421023421023421,1413002023421023421023421 %N A353144 Decimal repunits written in base 5. %F A353144 a(n) = A007091(A002275(n)). %o A353144 (PARI) a(n) = fromdigits(digits((10^n-1)/9, 5)); %Y A353144 Cf. A002275, A291962, A353142, A353143, A353145, A353146, A353147, A353148. %Y A353144 Cf. A003463, A007091. %K A353144 nonn,base,easy %O A353144 0,3 %A A353144 _Seiichi Manyama_, Apr 26 2022