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This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A188253 Number of arrangements of 7 nonzero numbers x(i) in -n..n with the sum of x(i)*x(i+1) equal to zero.

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%I A188253 #6 Jul 22 2025 11:05:52
%S A188253 40,1284,12692,58824,193232,521124,1142180,2347608,4323448,7567844,
%T A188253 12129300,19691552,29057776,42900188,61593740,86648240
%N A188253 Number of arrangements of 7 nonzero numbers x(i) in -n..n with the sum of x(i)*x(i+1) equal to zero.
%C A188253 Row 5 of A188249
%e A188253 Some solutions for n=4
%e A188253 ..1....2...-3...-1...-1....1...-1....4...-1....4...-1....4...-1....2....4....3
%e A188253 .-2....1....3....3...-2....1....3...-1....1....3....2....4...-3....3...-3...-2
%e A188253 ..4....4....4....3...-2....2....1...-4...-3...-3...-1....2...-3...-1...-4....1
%e A188253 ..2...-4...-4...-4...-2....3....2....3...-1....1....1...-2....4...-1...-1....4
%e A188253 .-3...-4...-4...-1....1...-2...-3....3....2....1....4....4....4...-2....4....2
%e A188253 .-4....3....3....2...-4....1...-4....3....1....1....1...-2...-2...-3...-3....4
%e A188253 ..1....2....3....2....1...-1....2...-2....1...-2...-3....2....4....4...-4...-3
%K A188253 nonn
%O A188253 1,1
%A A188253 _R. H. Hardin_ Mar 25 2011

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