A129996 - OEIS

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

(list; graph; refs; listen; history; text; internal format)

OFFSET

0,3

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

LINKS

Table of n, a(n) for n=0..35.

FORMULA

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

PROG

(PARI) A129996(n)=(-1)^((n+1)\2)*A000108(n\2+1) \\ - 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

Sequence in context: A056507 A285013 A095014 * A208355 A099363 A106181

Adjacent sequences: A129993 A129994 A129995 * A129997 A129998 A129999

KEYWORD

sign

AUTHOR

Paul Curtz, Jun 15 2007

EXTENSIONS

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

STATUS

approved