|
| |
|
|
A000492
|
|
Number of permutations of an n-sequence discordant with three given permutations (see reference) in n-6 places.
(Formerly M5092 N2204)
|
|
6
| |
|
|
20, 154, 1676, 14292, 155690, 1731708, 21264624, 280260864, 3970116255, 60113625680, 969368687752, 16588175089420, 300272980075896, 5733025551810600, 115148956467702600, 2427199940533198992, 53576182138937428377, 1235917889588345408586
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 6,1
|
|
|
REFERENCES
| J. Riordan, Discordant permutations, Scripta Math., 20 (1954), 14-23.
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
|
|
|
FORMULA
| a(n) = coefficient of y^6 in sum_0^n sigma_{n, k}(n - k)!(y - 1)^k on y where the sigma_{n, k} have generating function sigma(t, u)=(1 - 2t^2(u^2) - 2t^2(1 + t)u^3 + 3t^4(u^4))(1 - tu)^( - 1)(1 - (1 + 2t)u - tu^2 + t^3(u^3))^( - 1).
|
|
|
MAPLE
| seq(f(n, 6), n=6..30); #code for f(n, k) is given in A000440
|
|
|
CROSSREFS
| Cf. A000500, A000470, A000440, A000476, A000380, A000388.
Sequence in context: A022680 A108647 A164605 * A015866 A101091 A120693
Adjacent sequences: A000489 A000490 A000491 * A000493 A000494 A000495
|
|
|
KEYWORD
| nonn
|
|
|
AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
|
|
|
EXTENSIONS
| More terms, formula and Maple code from Barbara Haas Margolius (margolius(AT)math.csuohio.edu) 2/17/01
|
| |
|
|
