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%I #19 Jul 18 2022 09:49:51
%S 1,2,3,6,15,24,105,120,720,945,5040,10395,40320,135135,362880,2027025,
%T 3628800,34459425,39916800,479001600,654729075,6227020800,13749310575,
%U 87178291200,316234143225,1307674368000,7905853580625,20922789888000,213458046676875,355687428096000
%N Union of the factorial numbers (A000142) and the double factorials of odd numbers (A001147).
%D Douglas Hoftstadter, Keynote lecture, DIMACS Workshop on Recognition of Integer Sequences, Oct. 10, 2014.
%H <a href="http://dimacs.rutgers.edu/Workshops/OEIS/abstracts.html#hofstadter">Abstract of D. Hoftstadter in the Workshop's program</a>
%t max = 10^15;
%t A000142 = Reap[For[k = 0, k! <= max, k++, Sow[k!]]][[2, 1]];
%t A001147 = Reap[For[k = 1, k!! <= max, k = k+2, Sow[k!!]]][[2, 1]];
%t Union[A000142, A001147] (* _Jean-François Alcover_, Jul 18 2022 *)
%Y Cf. A000142, A001147, A005214.
%Y See A268645 for another version.
%K nonn
%O 1,2
%A _Olivier Gérard_, Oct 10 2014
%E Revised by _N. J. A. Sloane_, Feb 09 2016
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