|
Search: id:A073410
|
|
|
| A073410 |
|
Number of permutations p of (1,2,3,...,n) such that 1*(-1)^p(1)+2*(-1)^p(2)+3*(-1)^p(3)+...+n*(-1)^p(n)=0. |
|
+0
1
|
|
| 0, 0, 2, 8, 0, 0, 576, 4608, 0, 0, 2505600, 30067200, 0
(list; graph; listen)
|
|
|
OFFSET
|
1,3
|
|
|
FORMULA
|
It seems that a(n)=0 if n==1 or 2 (mod 4) and a(4*k)=4*k*a(4*k-1). - Benoit Cloitre (benoit7848c(AT)orange.fr), Aug 23 2002
|
|
PROGRAM
|
(PARI) a(n)=sum(k=1, n!, if(sum(i=1, n, i*(-1)^component(numtoperm(n, k), i)), 0, 1))
|
|
CROSSREFS
|
Sequence in context: A077548 A050809 A095217 this_sequence A021361 A073001 A088153
Adjacent sequences: A073407 A073408 A073409 this_sequence A073411 A073412 A073413
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
Benoit Cloitre (benoit7848c(AT)orange.fr), Aug 23 2002
|
|
EXTENSIONS
|
More terms from John W. Layman (layman(AT)math.vt.edu), Feb 05 2003
|
|
|
Search completed in 0.002 seconds
|
