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A180890 Number of permutations of 2..n+1 with no element greater than or equal to the sum of its neighbors 0
1, 0, 2, 6, 20, 90, 550, 3512, 25378, 200558, 1778156, 17016488, 177741892, 1984308356, 23873823014, 304944376412, 4155112842840 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Table of n, a(n) for n=1..17.

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

Sequence in context: A318813 A336544 A000666 * A027321 A027315 A005965

Adjacent sequences: A180887 A180888 A180889 * A180891 A180892 A180893

KEYWORD

nonn

AUTHOR

R. H. Hardin Sep 23 2010

STATUS

approved

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Last modified November 26 13:43 EST 2022. Contains 358362 sequences. (Running on oeis4.)