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 A307102 #27 Feb 16 2025 08:33:55 %S A307102 1,10,100,101,110,200,201,1000,1001,1010,1100,1101,1110,1200,10000, %T A307102 10001,10010,10100,10101,10110,10200,10201,11000,11001,11010,11100, %U A307102 11101,11110,11200,20000,20001,20010,20100,20101,20110,20200,20201,21000 %N A307102 Numbers written in base of double factorial numbers (A006882). %C A307102 a(1122755752855713895623244049306709034778906250) is the first term which cannot be included in the OEIS since it includes a non-decimal digit. - _Charles R Greathouse IV_, Sep 19 2012 %C A307102 Numbers in this mixed-radix number system can have multiple representations, so to avoid ambiguity this sequence assumes a greedy approach where leading digits are made as high as possible; thus we choose a(30) = 20000 rather than a(30) = 11201. - _Sean A. Irvine_, Mar 24 2019 %H A307102 Sean A. Irvine, <a href="/A307102/b307102.txt">Table of n, a(n) for n = 1..10000</a> %H A307102 F. Iacobescu, <a href="http://fs.unm.edu/FANELI.HTM">Smarandache Partition Type and Other Sequences</a>, Bull. Pure Appl. Sciences, Vol. 16E, No. 2 (1997), pp. 237-240. %H A307102 Sean A. Irvine, <a href="https://github.com/archmageirvine/joeis/blob/master/src/irvine/oeis/a307/A307102.java">Java program</a> (github). %H A307102 F. Smarandache, <a href="http://www.gallup.unm.edu/~smarandache/CP2.pdf">Collected Papers, Vol. II</a>. %H A307102 F. Smarandache, <a href="http://www.gallup.unm.edu/~smarandache/Sequences-book.pdf">Sequences of Numbers Involved in Unsolved Problems</a>. %H A307102 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/SmarandacheSequences.html">Smarandache Sequences</a>. %H A307102 <a href="/index/Fa#factorial">Index entries for sequences related to factorial numbers</a>. %e A307102 The digits (from right to left) have values 1, 2, 3, 8, 15, etc. (A006882), hence a(29) = 11200 because 29 = 1*15 + 1*8 + 2*3 + 0*2 + 0*1. %t A307102 a[n_] := FromDigits[NumberDecompose[n, Range[n, 1, -1]!!]]; Array[a, 40] (* _Amiram Eldar_, May 11 2024 *) %Y A307102 Cf. A006882 (double factorial numbers), A007623 (factorial base), A019513 (erroneous version). %K A307102 nonn,base %O A307102 1,2 %A A307102 _Sean A. Irvine_, Mar 24 2019