A027209 a(n) = Sum_{k=0..n-2} T(n,k) * T(n,k+2), with T given by A026725.

1, 7, 34, 173, 741, 3549, 14670, 68683, 279715, 1294598, 5233060, 24052965, 96822587, 442972139, 1778697948, 8110611295, 32516501991, 147897243768, 592346459071, 2688895275974, 10762289869782, 48776681304283, 195143578562778, 883272843800993, 3532739195660162

Offset

2,2

Links

Table of n, a(n) for n=2..26.

Maple

A027209 := proc(n)
    add( A026725(n, k)*A026725(n, k+2), k=0..n-2) ;
end proc: # R. J. Mathar, Oct 21 2019

Crossrefs

Sequence in context: A124466 A055271 A209890 * A209807 A351588 A080048

Adjacent sequences: A027206 A027207 A027208 * A027210 A027211 A027212

Keyword

nonn

Author

Clark Kimberling

Extensions

Name corrected by R. J. Mathar, Oct 21 2019

More terms from Sean A. Irvine, Oct 24 2019

Status

approved