A180070 - OEIS

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A180070

Number of permutations of {1..n} with the sum of squared adjacent differences <= n*(n+1)/2.

1, 1, 2, 6, 12, 44, 116, 374, 1428, 5960, 26016, 120570, 590598, 3065372, 16566508, 92827128, 542485764, 3298228302, 20696614200, 133722820270, 892046755174, 6136788856858, 43308637312440, 313079705562778, 2322726645160856

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OFFSET

0,3

LINKS

Table of n, a(n) for n=0..24.

CROSSREFS

Cf. A180071.

Sequence in context: A164859 A332868 A261467 * A177834 A169858 A292132

Adjacent sequences: A180067 A180068 A180069 * A180071 A180072 A180073

KEYWORD

nonn,hard

AUTHOR

R. H. Hardin, Aug 09 2010

EXTENSIONS

a(17)-a(18) from Donovan Johnson, Oct 11 2010

a(0)-a(1) from Alois P. Heinz, Sep 02 2020

a(19)-a(23) from Martin Ehrenstein, Nov 12 2023

a(24) from Max Alekseyev, Mar 15 2024

STATUS

approved