

A210541


Number of arrays of n nonnegative integers with value i>0 appearing only after i1 has appeared at least 4 times


4



1, 1, 1, 1, 2, 4, 8, 16, 33, 73, 177, 467, 1309, 3813, 11409, 34999, 110510, 361194, 1226930, 4334048, 15877297, 60049447, 233426007, 929616461, 3786970033, 15777120457, 67260334185, 293617319221, 1312868943154, 6010792180952
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OFFSET

1,5


COMMENTS



LINKS



FORMULA

a(n) = 1 if n<=4 else sum{i=0..n4}(binomial(n4,i)*a(i)). Proved by R. J. Mathar in the Sequence Fans Mailing List.


EXAMPLE

Some solutions for n=13
..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0
..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0
..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0
..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0
..1....1....1....0....1....1....1....0....1....1....0....0....1....0....0....1
..1....1....1....1....1....0....1....0....1....1....1....1....0....1....1....1
..0....1....0....0....1....0....1....0....0....0....0....1....0....0....1....0
..0....1....1....1....1....1....0....1....1....1....1....0....1....1....1....1
..1....2....1....0....0....1....1....1....1....1....0....0....1....1....1....0
..1....0....2....1....2....1....0....0....2....0....0....0....0....1....0....0
..0....1....1....1....2....2....1....1....1....0....0....1....0....2....2....1
..1....0....2....0....1....2....1....1....0....1....0....1....1....0....1....1
..2....0....1....2....1....0....2....2....2....0....0....1....2....0....2....0


CROSSREFS



KEYWORD

nonn


AUTHOR



STATUS

approved



