A129996 a(n) = (-1)^[(n+1)/2] A000108([n/2]+1).

1, -1, -2, 2, 5, -5, -14, 14, 42, -42, -132, 132, 429, -429, -1430, 1430, 4862, -4862, -16796, 16796, 58786, -58786, -208012, 208012, 742900, -742900, -2674440, 2674440, 9694845, -9694845, -35357670, 35357670, 129644790, -129644790, -477638700, 477638700

Offset: 0

Author

Paul Curtz, Jun 15 2007

Keywords

• sign

Comments

Terms of A000108(1,...) repeated, changing sign between the two repeated terms of same magnitude, but keeping the same sign for the next (larger) term. - M. F. Hasler, Aug 25 2012

Crossrefs

Cf. A099363, A106181 and A208355, which also consist of duplicated terms of A000108. - M. F. Hasler, Aug 25 2012

Programs

PARI

A129996(n)=(-1)^((n+1)\2)*A000108(n\2+1) \\ - M. F. Hasler, Aug 25 2012

Formula

First differences of A129110: a(n)=A129110(n+1)-A129110(n).

Extensions

Definition (formula) corrected by M. F. Hasler, Aug 25 2012