0,3

a(n)=(4-3n(-2)^(n-1)+5(-2)^n)/9; a(n)=(1/4)+sum{k=0..n, (-2)^k(k+3)/4 }; G.f.: (1+x)^2/((1-x)(1+2x)^2).

Sequence in context: A047196 A009889 A095804 this_sequence A009916 A123861 A115099

Adjacent sequences: A084216 A084217 A084218 this_sequence A084220 A084221 A084222

easy,sign

Paul Barry (pbarry(AT)wit.ie), May 20 2003