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A005991 Let k(m) denote the least integer such that every m X m (0,1)-matrix with exactly k(m) ones in each row and in each column contains a 2 X 2 submatrix without zeros. The sequence gives the index n of the last term in each string of equal entries in the {k(m)} sequence (see A155934).
(Formerly M1582)
2
2, 6, 12, 20, 30, 43 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
REFERENCES
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
LINKS
E. T. Wang and R. K. Guy, Problem E2429, Amer. Math. Monthly, 81 (1974), 1112-1113.
FORMULA
a(n) = A003509(n + 1) - 1. - Sean A. Irvine, Jun 04 2015
EXAMPLE
Since k(2) = 2 then a(1) = 2
Since k(3) = k(4) = k(5) = k(6) = 3 then a(2) = 6
Since k(7) = k(8) = ... = k(12) = 4 then a(3) = 12
Since k(13) = k(14) = ... = k(20) = 5 then a(4) = 20
Since k(21) = k(22) = ... = k(30) = 6 then a(5) = 30
Since k(31) = k(32) = ... = k(43) = 7 then a(6) = 43
CROSSREFS
Cf. A003509 (index of first term), A155934.
Sequence in context: A279019 A002378 A349704 * A266194 A194110 A291876
KEYWORD
nonn,more
AUTHOR
EXTENSIONS
Edited by Herman Jamke (hermanjamke(AT)fastmail.fm), Mar 02 2008
STATUS
approved

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Last modified March 19 03:18 EDT 2024. Contains 370952 sequences. (Running on oeis4.)