A248652 - OEIS

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

(list; graph; refs; listen; history; text; internal format)

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]];