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 A045207 #20 May 21 2023 00:19:12 %S A045207 20,29,45,54,70,79,95,101,102,103,105,110,115,134,139,144,146,147,148, %T A045207 154,170,179,195,204,220,226,227,228,230,235,240,259,264,269,271,272, %U A045207 273,279,295,304,320,329,345,351,352,353,355 %N A045207 Numbers whose base-5 representation contains exactly one 0 and one 4. %C A045207 Subset of A039286. - _R. J. Mathar_, Oct 20 2008 %H A045207 Robert Israel, <a href="/A045207/b045207.txt">Table of n, a(n) for n = 1..10000</a> %p A045207 F:= proc(d) local S, i,j; %p A045207 # to get all d-digit members %p A045207 S:= select(t -> t[d]<>0, map(op@combinat:-permute,[seq(seq([0,4,1$i,2$j,3$(d-2-i-j)],j=0..d-2-i),i=0..d-2)])); %p A045207 sort(map(t -> add(t[i]*5^(i-1),i=1..d), S)) %p A045207 end proc: %p A045207 seq(op(F(d)),d=2..5); # _Robert Israel_, Aug 02 2020 %t A045207 Select[Range[400],DigitCount[#,5,0]==DigitCount[#,5,4]==1&] (* _Harvey P. Dale_, Nov 10 2017 *) %Y A045207 Cf. A007091. %K A045207 nonn,base %O A045207 1,1 %A A045207 _Clark Kimberling_