A180890 - OEIS

A180890

Number of permutations of 2..n+1 with no element greater than or equal to the sum of its neighbors

1, 0, 2, 6, 20, 90, 550, 3512, 25378, 200558, 1778156, 17016488, 177741892, 1984308356, 23873823014, 304944376412, 4155112842840

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OFFSET

1,3

LINKS

EXAMPLE

All solutions for n=5

(2 3 4 6 5) (2 3 5 6 4) (2 3 6 5 4) (2 4 3 6 5)

(2 4 5 6 3) (2 4 6 5 3) (2 5 4 6 3) (2 5 6 4 3)

(2 6 5 4 3) (3 4 2 6 5) (3 4 5 6 2) (3 4 6 5 2)

(3 5 6 4 2) (3 6 4 5 2) (3 6 5 4 2) (4 5 6 3 2)

(4 6 5 3 2) (5 6 2 4 3) (5 6 3 4 2) (5 6 4 3 2)

CROSSREFS

KEYWORD

nonn

AUTHOR

STATUS

approved