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A268645
Union of the factorial numbers (A000142) and the double factorials numbers (A006882).
1
1, 2, 3, 6, 8, 15, 24, 48, 105, 120, 384, 720, 945, 3840, 5040, 10395, 40320, 46080, 135135, 362880, 645120, 2027025, 3628800, 10321920, 34459425, 39916800, 185794560, 479001600, 654729075, 3715891200, 6227020800, 13749310575, 81749606400, 87178291200, 316234143225, 1307674368000
OFFSET
1,2
REFERENCES
Douglas Hoftstadter, Keynote lecture, DIMACS Workshop on Recognition of Integer Sequences, Oct. 10, 2014.
MATHEMATICA
max = 10^13;
A000142 = Reap[For[k = 0, k! <= max, k++, Sow[k!]]][[2, 1]];
A006882 = Reap[For[k = 0, k!! <= max, k++, Sow[k!!]]][[2, 1]];
Union[A000142, A006882] (* Jean-François Alcover, Jul 18 2022 *)
CROSSREFS
See A248652 for another version.
Sequence in context: A209405 A048809 A300671 * A047001 A174021 A267007
KEYWORD
nonn
AUTHOR
Olivier Gérard, Oct 10 2014, revised by N. J. A. Sloane, Feb 09 2016
STATUS
approved