|
| |
|
|
A005744
|
|
G.f.: x*(1+x-x^2)/((1-x)^4*(1+x)).
(Formerly M3360)
|
|
11
| |
|
|
0, 1, 4, 9, 17, 28, 43, 62, 86, 115, 150, 191, 239, 294, 357, 428, 508, 597, 696, 805, 925, 1056, 1199, 1354, 1522, 1703, 1898, 2107, 2331, 2570, 2825, 3096, 3384, 3689, 4012, 4353, 4713, 5092, 5491, 5910, 6350, 6811, 7294, 7799, 8327, 8878, 9453, 10052
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 0,3
|
|
|
COMMENTS
| Number of n-covers of a 2-set.
a(n)=A002623(n)-(n+1).
Boolean switching functions a(n,s) for s = 2.
|
|
|
REFERENCES
| R. J. Clarke, Covering a set by subsets, Discrete Math., 81 (1990), 147-152.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
|
|
|
LINKS
| T. D. Noe, Table of n, a(n) for n=0..1000
Vladeta Jovovic, Binary matrices up to row and column permutations
Index entries for sequences related to linear recurrences with constant coefficients
Index entries for sequences related to Boolean functions
|
|
|
FORMULA
| a(n) = n*(n-1)/2 + Sum((n-2*i+1)*(n-2*i)/2, i=1..floor( (n+1)/2 )). - N. J. A. Sloane (njas(AT)research.att.com), Nov 28 2003
a(n) = 5*n/12-1/16+5*n^2/8+n^3/12+(-1)^n/16 . a(n)= 3*a(n-1) -2*a(n-2) -2*a(n-3) +3*a(n-4) -a(n-5). [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Apr 01 2010]
|
|
|
CROSSREFS
| John Layman (layman(AT)calvin.math.vt.edu) observes that A003453 appears to be the alternating sum transform (PSumSIGN) of A005744.
Cf. A002623, A005745, A005746, A005747, A005748, A005771, A003180.
Cf. A052265.
Sequence in context: A008023 A008055 A137441 * A027367 A009879 A009878
Adjacent sequences: A005741 A005742 A005743 * A005745 A005746 A005747
|
|
|
KEYWORD
| easy,nonn,nice
|
|
|
AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Simon Plouffe (simon.plouffe(AT)gmail.com)
|
|
|
EXTENSIONS
| Additional comments from Alford Arnold (Alford1940(AT)aol.com)
More terms from Vladeta Jovovic (vladeta(AT)eunet.rs), May 25 2000
|
| |
|
|
