OFFSET
2,2
COMMENTS
This is a lower bound for the set of all n X n (0,1)-matrices having distinct, nonzero ordered rows and determinant 0 (compare A000410).
Here ordered means that we take only one representative from the n! matrices obtained by all permutations of the distinct rows of an n X n matrix.
a(n) is also the number of sets of n distinct nonzero (0,1)-vectors in R^n that do not span R^n.
REFERENCES
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).
LINKS
J. Kahn, J. Komlos and E. Szemeredi, On the probability that a random ±1-matrix is singular, J. AMS 8 (1995), 223-240.
Goran Kilibarda and Vladeta Jovovic, Enumeration of some classes of T_0-hypergraphs, arXiv:1411.4187 [math.CO], 2014.
J. Komlos, On the determinant of (0,1)-matrices, Studia Math. Hungarica 2 (1967), 7-21.
N. Metropolis and P. R. Stein, On a class of (0,1) matrices with vanishing determinants, J. Combin. Theory, 3 (1967), 191-198.
FORMULA
a(n) = (-1)*Sum_{k=0..n-1} Stirling1(n+1, k+1)*binomial(2^k-1, n).
a(n) = binomial(2^n-1, n) - A094000(n). - Vladeta Jovovic, Nov 27 2005
MAPLE
with(combinat): T := proc(n) -sum(stirling1(n+1, k+1)*binomial(2^k-1, n), k=0..n-1); end proc:
MATHEMATICA
a[n_] := -Sum[ StirlingS1[n+1, k+1]*Binomial[2^k-1, n], {k, 0, n-1}]; Table[a[n], {n, 2, 15}] (* Jean-François Alcover, Nov 21 2012, from formula *)
PROG
(PARI) a(n) = -sum(k=0, n-1, stirling(n+1, k+1, 1)*binomial(2^k-1, n)); \\ Michel Marcus, Jun 05 2020
(Magma) [ -(&+[StirlingFirst(n+1, k+1)*Binomial(2^k-1, n): k in [0..n-1]]): n in [2..15]]; // G. C. Greubel, Jun 05 2020
(Sage) [sum((-1)^(n+k+1)*stirling_number1(n+1, k+1)*binomial(2^k-1, n) for k in (0..n-1)) for n in (2..15)] # G. C. Greubel, Jun 05 2020
CROSSREFS
KEYWORD
nonn,nice
AUTHOR
EXTENSIONS
Edited by W. Edwin Clark, Nov 02 2003
STATUS
approved