A129937 a(n) = binomial(n, floor(n/2)) - n*(n - 1)/2.

1, 1, 0, 0, 0, 5, 14, 42, 90, 207, 407, 858, 1638, 3341, 6330, 12750, 24174, 48467, 92207, 184566, 352506, 705201, 1351825, 2703880, 5200000, 10400275, 20057949, 40116222, 77558354, 155117085, 300539730, 601079894, 1166802582, 2333605659, 4537567055, 9075134670, 17672631234, 35345263097, 68923263669, 137846528040, 269128936400, 538257873579

Offset

1,6

Links

Table of n, a(n) for n=1..42.

Formula

a(n) = binomial(n, floor(n/2)) - n*(n - 1)/2 = A001405(n) - A000217(n-1).

Mathematica

a[n_] = Binomial[n, Floor[n/2]] - n*(n - 1)/2; Table[a[n], {n, 1, 30}]

Crossrefs

Cf. A000217, A001405.

Sequence in context: A270893 A272316 A032249 * A147978 A266941 A034549

Adjacent sequences: A129934 A129935 A129936 * A129938 A129939 A129940

Keyword

nonn,less,easy,changed

Author

Roger L. Bagula, Jun 09 2007

Status

approved