A158155 Number of nondecreasing integer sequences of length 21 with sum zero and sum of absolute values 2n.

1, 4, 9, 25, 49, 121, 225, 484, 900, 1764, 3135, 5921, 10163, 18086, 30544, 52168, 85231, 141308, 225085, 361916, 565231, 884209, 1351340, 2071388, 3105033, 4656911, 6869566, 10115584, 14675797, 21268848, 30402838, 43382123, 61208590, 86112584, 119960832, 166699764

Offset

1,2

Links

R. H. Hardin, Table of n, a(n) for n=1..304

Formula

a(n) = A000041(n)^2 for n <= 10.

a(n) = A000041(n)^2 - cumulative A000712(2*n-1-length), 0 <= 2*n-1-length <= floor(n/2) [empirical].

Crossrefs

Column k=21 of A389686.

Sequence in context: A158152 A158153 A158154 * A158156 A158157 A158158

Adjacent sequences: A158152 A158153 A158154 * A158156 A158157 A158158

Keyword

nonn

Author

R. H. Hardin, Mar 13 2009

Status

approved