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 A023725 #17 Apr 14 2025 05:33:23
%S A023725 0,2,3,4,10,12,13,14,15,17,18,19,20,22,23,24,50,52,53,54,60,62,63,64,
%T A023725 65,67,68,69,70,72,73,74,75,77,78,79,85,87,88,89,90,92,93,94,95,97,98,
%U A023725 99,100,102,103,104,110,112,113,114,115,117,118,119,120
%N A023725 Numbers with no 1's in their base-5 expansion.
%H A023725 Nathaniel Johnston, <a href="/A023725/b023725.txt">Table of n, a(n) for n = 1..10000</a>
%H A023725 Robert Baillie and Thomas Schmelzer, <a href="https://library.wolfram.com/infocenter/MathSource/7166/">Summing Kempner's Curious (Slowly-Convergent) Series</a>, Mathematica Notebook kempnerSums.nb, Wolfram Library Archive, 2008.
%H A023725 <a href="/index/Ar#5-automatic">Index entries for 5-automatic sequences</a>.
%F A023725 Sum_{n>=2} 1/a(n) = 4.7113203882192880160403245816366085015069192113921100121384809791433027046475062716543062654277431569224... (calculated using Baillie and Schmelzer's kempnerSums.nb, see Links). - _Amiram Eldar_, Apr 14 2025
%p A023725 seq(`if`(numboccur(1,convert(n,base,5))=0,n,NULL),n=0..127); # _Nathaniel Johnston_, Jun 27 2011
%t A023725 Select[ Range[ 0, 125 ], (Count[ IntegerDigits[ #, 5 ], 1 ]==0)& ]
%t A023725 Select[Range[0, 120], DigitCount[#, 5, 1] == 0 &] (* _Amiram Eldar_, Apr 14 2025 *)
%o A023725 (PARI) is(n)=while(n>1, if(n%5==1, return(0)); n\=5); 1 \\ _Charles R Greathouse IV_, Feb 12 2017
%Y A023725 Cf. A020654, A023721, A023729, A023733.
%K A023725 nonn,base,easy
%O A023725 1,2
%A A023725 _Olivier Gérard_