A187981 Number of nondecreasing arrangements of n numbers x(i) in -n..n with the sum of sign(x(i))*2^|x(i)| zero.

0, 2, 5, 15, 57, 181, 632, 2199, 7593, 26706, 93724, 330555, 1170088, 4149361, 14754670, 52564714, 187595025, 670589799, 2400467901, 8603906865, 30874479617, 110907636467, 398789645747, 1435195800184, 5169318396770, 18633022691923, 67210498566801, 242590233305619, 876138147816208, 3166048659124955, 11447024096561941, 41407915745717488

Offset

1,2

Links

Table of n, a(n) for n=1..32.

Example

All solutions for n=3:
.-1...-2...-3...-2...-1
..0....1....2...-2...-1
..0....1....2....3....2

Crossrefs

Column 2 of A187988.

Sequence in context: A216388 A005976 A351158 * A334155 A373768 A348365

Adjacent sequences: A187978 A187979 A187980 * A187982 A187983 A187984

Keyword

nonn

Author

R. H. Hardin, Mar 18 2011

Extensions

More terms from R. J. Mathar, May 11 2023

Status

approved