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Numbers written in base of double factorial numbers (A006882).
2

%I #26 May 11 2024 09:15:57

%S 1,10,100,101,110,200,201,1000,1001,1010,1100,1101,1110,1200,10000,

%T 10001,10010,10100,10101,10110,10200,10201,11000,11001,11010,11100,

%U 11101,11110,11200,20000,20001,20010,20100,20101,20110,20200,20201,21000

%N Numbers written in base of double factorial numbers (A006882).

%C 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 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 Sean A. Irvine, <a href="/A307102/b307102.txt">Table of n, a(n) for n = 1..10000</a>

%H 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 Sean A. Irvine, <a href="https://github.com/archmageirvine/joeis/blob/master/src/irvine/oeis/a307/A307102.java">Java program</a> (github).

%H F. Smarandache, <a href="http://www.gallup.unm.edu/~smarandache/CP2.pdf">Collected Papers, Vol. II</a>.

%H F. Smarandache, <a href="http://www.gallup.unm.edu/~smarandache/Sequences-book.pdf">Sequences of Numbers Involved in Unsolved Problems</a>.

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/SmarandacheSequences.html">Smarandache Sequences</a>.

%H <a href="/index/Fa#factorial">Index entries for sequences related to factorial numbers</a>.

%e 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 a[n_] := FromDigits[NumberDecompose[n, Range[n, 1, -1]!!]]; Array[a, 40] (* _Amiram Eldar_, May 11 2024 *)

%Y Cf. A006882 (double factorial numbers), A007623 (factorial base), A019513 (erroneous version).

%K nonn,base

%O 1,2

%A _Sean A. Irvine_, Mar 24 2019