A139149 a(n) = (n!+2)/2.

2, 4, 13, 61, 361, 2521, 20161, 181441, 1814401, 19958401, 239500801, 3113510401, 43589145601, 653837184001, 10461394944001, 177843714048001, 3201186852864001, 60822550204416001, 1216451004088320001, 25545471085854720001, 562000363888803840001

Offset

2,1

Comments

Also the number of (not necessarily maximal) cliques in the (n-1)-(weak) Bruhat graph. - Eric W. Weisstein, Jul 29 2018

Links

Amiram Eldar, Table of n, a(n) for n = 2..450

Eric Weisstein's World of Mathematics, Bruhat Graph.

Eric Weisstein's World of Mathematics, Clique.

Example

(1!+2)/2 = 3/2 is not an integer.
a(2) = (2!+2)/2 = 2.

Mathematica

Table[(n! + 2)/2, {n, 2, 30}]

Prog

(PARI) a(n)=n!/2+1 \\ Charles R Greathouse IV, Jun 20 2012

Crossrefs

a(n) = (n!+m)/m: A038507 (m=1), this sequence (m=2), A139150 (m=3), A139151 (m=4), A139152 (m=5), A139153 (m=6), A139154 (m=7), A139155 (m=8), A139156 (m=9), A139157 (m=10).

Offsets for above sequences are Kempner numbers A002034.

For smallest number of the form (m!+n)/n see A139148.

Cf. A007749, A020458, A082672, A089085, A089130, A117141, A137390, A139056-A139066, A139068, A139070-A139075, A139157, A139159-A139162.

Sequence in context: A201691 A020120 A020097 * A297861 A298128 A132786

Adjacent sequences: A139146 A139147 A139148 * A139150 A139151 A139152

Keyword

nonn,easy

Author

Artur Jasinski, Apr 11 2008

Status

approved