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.
%I A188349 #7 Jul 22 2025 11:09:07 %S A188349 5,45,257,4201,45801,1171345,25217201,870473329,30807035021, %T A188349 1370460938381 %N A188349 Number of arrangements of n+1 numbers x(i) in -n..n with the sum of x(i)*x(i+1) equal to zero. %C A188349 Diagonal of A188358 %e A188349 Some solutions for n=4 %e A188349 ..2...-2...-3....1....0....4....4....2...-4...-3...-1....4....2...-4...-2....4 %e A188349 ..0....1...-4....2...-3....1....2....1...-2....0...-4....0....0....4...-1....4 %e A188349 .-1....3....2...-4...-3....2...-4...-2....1....1....0...-2...-2....4...-1...-3 %e A188349 .-1...-1...-4...-1....3...-1....1...-1....3....0....1....2....2....0....1....2 %e A188349 ..1...-2...-1...-2....0....4....4....2...-3...-4...-4....2....2....2...-2....1 %K A188349 nonn %O A188349 1,1 %A A188349 _R. H. Hardin_ Mar 28 2011