

A213121


Number of binary arrays of length 2*n+3 with fewer than n ones in any length 2n subsequence (=less than 50% duty cycle).


1



1, 14, 86, 424, 1926, 8404, 35836, 150604, 626726, 2589844, 10646676, 43594464, 177950236, 724578824, 2944375096, 11944652884, 48388816486, 195794585044, 791434666276, 3196307541904, 12898839944116, 52019043912664
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,2


COMMENTS



LINKS



FORMULA

Recurrence: n*(7*n19)*a(n) = 2*(28*n^297*n+60)*a(n1)  8*(2*n5)*(7*n12) * a(n2).  Vaclav Kotesovec, Oct 19 2012


EXAMPLE

Some solutions for n=3
..0....0....1....0....0....0....0....0....0....0....1....1....1....1....0....1
..0....0....0....0....0....1....0....1....1....0....1....0....0....0....0....0
..1....1....0....0....0....0....0....0....0....0....0....0....0....0....0....0
..0....0....0....1....0....0....0....1....0....1....0....0....0....0....0....1
..1....0....1....0....1....1....0....0....1....1....0....0....0....0....0....0
..0....0....0....0....1....0....0....0....0....0....0....0....1....0....0....0
..0....0....0....0....0....0....0....0....0....0....1....0....0....1....0....0
..0....1....0....1....0....0....0....0....0....0....0....1....1....0....1....0
..0....1....1....0....0....1....0....0....0....0....0....1....0....0....1....0


MATHEMATICA

Table[2^(2*n+2)5*(7*n4)*Binomial[2*n2, n1]/n, {n, 1, 20}] (* Vaclav Kotesovec, Oct 29 2012 *)


CROSSREFS



KEYWORD

nonn


AUTHOR



STATUS

approved



