

A284757


Number of solutions to Nickerson variant of quadruples version of Langford (or LangfordSkolem) problem.


2



1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 10, 55, 0, 0, 0, 0, 0, 0
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OFFSET

1,24


COMMENTS

How many ways are of arranging the numbers 1,1,1,1,2,2,2,2,3,3,3,3,...,n,n,n,n so that there are zero numbers between the first and second 1's, between the second and third 1's and between the third and fourth 1's; one number between the first and second 2's, between the second and third 2's and between the third and fourth 2's; ... n1 numbers between the first and second n's, between the second and third n's and between the third and fourth n's?
An equivalent definition is A261517 with added condition that all different common intervals are <= n.
a(n) ignores reflected solutions.


LINKS



FORMULA

a(n) = 0 if (n mod 8) not in {0, 1}.  Max Alekseyev, Sep 28 2023


CROSSREFS



KEYWORD

nonn,more


AUTHOR



EXTENSIONS



STATUS

approved



