A131119 a(n) = (-1)^n * Sum_{i=1..floor(n/2)} i * floor(n/(n-i)).

0, 0, 2, -1, 5, -3, 9, -6, 14, -10, 20, -15, 27, -21, 35, -28, 44, -36, 54, -45, 65, -55, 77, -66, 90, -78, 104, -91, 119, -105, 135, -120, 152, -136, 170, -153, 189, -171, 209, -190, 230, -210, 252, -231, 275, -253, 299, -276, 324, -300, 350, -325, 377, -351, 405

Offset

0,3

Comments

Alternate A000096 and -A000217. Differences: A131723.

Links

Table of n, a(n) for n=0..54.

Mathematica

Table[(-1)^n*Sum[i*Floor[n/(n - i)], {i, Floor[n/2]}], {n, 0, 80}] (* Wesley Ivan Hurt, Nov 26 2020 *)

Crossrefs

Cf. A000096, A000217, A131723.

Sequence in context: A334172 A085261 A179218 * A114901 A355562 A194809

Adjacent sequences: A131116 A131117 A131118 * A131120 A131121 A131122

Keyword

sign,easy

Author

Paul Curtz, Sep 24 2007

Extensions

New name and more terms from Wesley Ivan Hurt, Nov 26 2020

Status

approved