A268645 Union of the factorial numbers (A000142) and the double factorials numbers (A006882).

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.

Links

Table of n, a(n) for n=1..36.

Abstract of D. Hoftstadter in the Workshop's program

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

Cf. A000142, A006882.

See A248652 for another version.

Sequence in context: A209405 A048809 A300671 * A047001 A174021 A267007

Adjacent sequences: A268642 A268643 A268644 * A268646 A268647 A268648

Keyword

nonn

Author

Olivier Gérard, Oct 10 2014, revised by N. J. A. Sloane, Feb 09 2016

Status

approved