A158154 Number of nondecreasing integer sequences of length 20 with sum zero and sum of absolute values 2n.

1, 4, 9, 25, 49, 121, 225, 484, 900, 1764, 3133, 5911, 10127, 17976, 30254, 51476, 83727, 138214, 219057, 350478, 544347, 846845, 1286514, 1960520, 2920291, 4352663, 6378968, 9332660, 13448845, 19362348, 27487400, 38958013, 54584986

Offset

1,2

Links

R. H. Hardin, Table of n, a(n) for n=1..327

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=20 of A389686.

Sequence in context: A158151 A158152 A158153 * A158155 A158156 A158157

Adjacent sequences: A158151 A158152 A158153 * A158155 A158156 A158157

Keyword

nonn

Author

R. H. Hardin, Mar 13 2009

Status

approved