A074660 Second differences of A074658, which counts the convex partitions of n.

1, 0, 1, -1, 2, 0, -2, 3, 2, -4, 3, 2, -6, 9, 3, -13, 6, 12, -14, 12, -1, -13, 14, 9, -14, 8, 4, -8, 6, 16, -37, 35, 10, -25, 19, 10, -45, 34, 30, -27, -8, 35, -37, 36, 8, -37, 21, 37, -51, 53, 1, -56, 41, 68, -79, 13, 29, -23, 16, 87, -98, 40, 38, -70, 43, 53, -81, 81, 35, -61, -28, 140, -132, 87, 80, -118, 5

Offset

0,5

Comments

Up to n=246, the signs of the terms show some periodicity (mod 3): a(3n) is almost always negative and a(3n+2) is almost always positive. Does this continue?

Links

Table of n, a(n) for n=0..76.

Formula

a(n) = A074659(n+1)-A074659(n) = A074658(n+2)-2*A074658(n+1)+A074658(n)

Mathematica

Table[a[n+2]-2a[n+1]+a[n], {n, 0, 76}] (* a[n] is defined in A074658. *)

Crossrefs

Cf. A074658, A074659.

Sequence in context: A371571 A033769 A333636 * A002125 A171731 A323212

Adjacent sequences: A074657 A074658 A074659 * A074661 A074662 A074663

Keyword

sign

Author

Dean Hickerson, Aug 29 2002

Status

approved