A248652 Union of the factorial numbers (A000142) and the double factorials of odd numbers (A001147).

1, 2, 3, 6, 15, 24, 105, 120, 720, 945, 5040, 10395, 40320, 135135, 362880, 2027025, 3628800, 34459425, 39916800, 479001600, 654729075, 6227020800, 13749310575, 87178291200, 316234143225, 1307674368000, 7905853580625, 20922789888000, 213458046676875, 355687428096000

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..30.

Abstract of D. Hoftstadter in the Workshop's program

Mathematica

max = 10^15;
A000142 = Reap[For[k = 0, k!  <= max, k++, Sow[k!]]][[2, 1]];
A001147 = Reap[For[k = 1, k!! <= max, k = k+2, Sow[k!!]]][[2, 1]];
Union[A000142, A001147] (* Jean-François Alcover, Jul 18 2022 *)

Crossrefs

Cf. A000142, A001147, A005214.

See A268645 for another version.

Sequence in context: A081945 A329745 A255353 * A158027 A346776 A371570

Adjacent sequences: A248649 A248650 A248651 * A248653 A248654 A248655

Keyword

nonn

Author

Olivier Gérard, Oct 10 2014

Extensions

Revised by N. J. A. Sloane, Feb 09 2016

Status

approved