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

Table of n, a(n) for n=2..22.

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

Numbers of the form (n!+m)/m:

m=1 numbers of the form (n!+1)/1 see A038507

m=2 (this sequence)

m=3 numbers of the form (n!+3)/3 see A139150

m=4 numbers of the form (n!+4)/4 see A139151

m=5 numbers of the form (n!+5)/5 see A139152

m=6 numbers of the form (n!+6)/6 see A139153

m=7 numbers of the form (n!+7)/7 see A139154

m=8 numbers of the form (n!+8)/8 see A139155

m=9 numbers of the form (n!+9)/9 see A139156

m=10 numbers of the form (n!+10)/10 see A139157

Offsets for above sequences are Kempner numbers A002034.

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

Cf. A082672, A089085, A089130, A117141, A007749, A139056-A139066, A020458, A139068, A137390, A139070-A139075, A139148, A139149, 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