1,2

G.f.: [1+2x+x^2+x^3]/[(1-x)^2*(1+x+x^2)].

a(2) = 4, a(0) = 1, a(1) = 3, (-13-5*n)*a(n)-5*a(n+1)-5*a(n+2)+(5*n+8)*a(n+3). a(n)= 1+(5 n)/3-(i sqrt(3) (-1/2+(i sqrt(3))/2)^n)/9+(i sqrt(3) (-1/2-(i sqrt(3))/2)^n)/9 - Stephen Crowley (crow(AT)crowlogic.net), Feb 11 2007

Sequence in context: A109259 A059535 A061402 this_sequence A081031 A133280 A138097

Adjacent sequences: A047203 A047204 A047205 this_sequence A047207 A047208 A047209

nonn

N. J. A. Sloane (njas(AT)research.att.com).