A024853 a(n) = s(1)t(n) + s(2)t(n-1) + ... + s(k)t(n-k+1), where k = [ n/2 ], s = (natural numbers), t = (natural numbers >= 2).

3, 4, 13, 16, 34, 40, 70, 80, 125, 140, 203, 224, 308, 336, 444, 480, 615, 660, 825, 880, 1078, 1144, 1378, 1456, 1729, 1820, 2135, 2240, 2600, 2720, 3128, 3264, 3723, 3876, 4389, 4560, 5130, 5320, 5950, 6160, 6853, 7084, 7843, 8096, 8924, 9200, 10100, 10400

Offset

2,1

Links

Table of n, a(n) for n=2..49.

Formula

a(n) = m * (m+1) * (3*n+5-2*m) / 6 where m = floor(n/2). - Sean A. Irvine, Jul 26 2019

Crossrefs

Sequence in context: A293280 A087884 A057570 * A023857 A323149 A291250

Adjacent sequences: A024850 A024851 A024852 * A024854 A024855 A024856

Keyword

nonn

Author

Clark Kimberling

Status

approved