A111300 Positive integers that are the difference between two double factorials.

0, 1, 2, 5, 6, 7, 12, 13, 14, 33, 40, 45, 46, 47, 57, 90, 97, 102, 103, 104, 279, 336, 369, 376, 381, 382, 383, 561, 840, 897, 930, 937, 942, 943, 944, 2895, 3456, 3735, 3792, 3825, 3832, 3837, 3838, 3839, 6555, 9450, 10011, 10290, 10347, 10380, 10387, 10392

Offset

1,3

Links

T. D. Noe, Table of n, a(n) for n = 1..1000

Formula

M!! - N!! where M and N positive integers.

Example

7!! - 4!! = 7*5*3*1 - 4*2 = 105 - 8 = 97.
9!! - 5!! = 9*7*5*3*1 - 5*3*1 = 945 - 15 = 930.

Mathematica

terms[n_]:=Sort[Union[Flatten[Table[j!!-i!!, {i, n}, {j, i, n}]]]]; terms[12] (* Enrique Pérez Herrero, May 21 2011 *)

Crossrefs

Cf. A006882 (n!!).

Sequence in context: A103025 A134080 A342792 * A215761 A117548 A175135

Adjacent sequences: A111297 A111298 A111299 * A111301 A111302 A111303

Keyword

easy,nonn

Author

Paolo P. Lava and Giorgio Balzarotti, Nov 02 2005

Extensions

Extended by T. D. Noe, May 22 2011

Status

approved