|
Search: id:A062119
|
|
| |
|
| 0, 2, 12, 72, 480, 3600, 30240, 282240, 2903040, 32659200, 399168000, 5269017600, 74724249600, 1133317785600, 18307441152000, 313841848320000, 5690998849536000, 108840352997376000, 2189611807358980000
(list; graph; listen)
|
|
|
OFFSET
|
1,2
|
|
|
COMMENT
|
For n>0 a(n) = number of permutations of length n+1 that have 2 predetermined elements non-adjacent, e.g. for n=2, the permutations with say 1 and 2 non-adjacent are 132 and 231, therefore a(2)=2. - Jon Perry (perry(AT)globalnet.co.uk), Jun 08 2003
|
|
LINKS
|
Milan Janjic, Enumerative Formulas for Some Functions on Finite Sets
|
|
MAPLE
|
a:=n->sum(n!, j=2..n):seq(a(n), n=1..19); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Apr 30 2007
seq(sum(mul(j, j=1..n), k=2..n), n=1..19); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jun 01 2007
a:=n->add((n!), j=1..n-1):seq(a(n), n=1..21); [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Aug 27 2008]
|
|
CROSSREFS
|
Cf. A018931.
a(n)=2*A001286(n). Cf. A052849.
Sequence in context: A002670 A119921 A018931 this_sequence A052556 A052833 A005443
A001563 [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Aug 27 2008]
Adjacent sequences: A062116 A062117 A062118 this_sequence A062120 A062121 A062122
|
|
KEYWORD
|
easy,nonn
|
|
AUTHOR
|
Olivier Gerard (ogerard(AT)ext.jussieu.fr), Jun 13 2001
|
|
|
Search completed in 0.002 seconds
|
