A005214 -id:A005214 - cp's OEIS frontend

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

Olivier Gérard, Oct 10 2014

nonn

Douglas Hoftstadter, Keynote lecture, DIMACS Workshop on Recognition of Integer Sequences, Oct. 10, 2014.

Abstract of D. Hoftstadter in the Workshop's program

Cf. A000142, A001147, A005214.

See A268645 for another version.

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 *)

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

A342469 Positive numbers that are triangular, square or pentagonal.

Original entry on oeis.org

1, 3, 4, 5, 6, 9, 10, 12, 15, 16, 21, 22, 25, 28, 35, 36, 45, 49, 51, 55, 64, 66, 70, 78, 81, 91, 92, 100, 105, 117, 120, 121, 136, 144, 145, 153, 169, 171, 176, 190, 196, 210, 225, 231, 247, 253, 256, 276, 287, 289, 300, 324, 325, 330, 351, 361, 376, 378, 400

Offset: 1

Michel Marcus, Mar 13 2021

nonn

Cf. A000290, A000217, A000326, A005214.

Cf. A245646, A245647, A245648.

isok(m) = ispolygonal(m,3) || ispolygonal(m,4) || ispolygonal(m,5);

cp's OEIS Frontend

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

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