A099214 a(n)=4a(n-1)-4a(n-2)+4a(n-3).

1, 2, 4, 12, 40, 128, 400, 1248, 3904, 12224, 38272, 119808, 375040, 1174016, 3675136, 11504640, 36014080, 112738304, 352915456, 1104764928, 3458351104, 10826006528, 33889681408, 106088103936, 332097716224, 1039597174784

Offset

0,2

Comments

Binomial transform of A099213.

Links

Table of n, a(n) for n=0..25.

Formula

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

Crossrefs

Cf. A073724.

Sequence in context: A170809 A170808 A366579 * A126946 A113179 A214761

Adjacent sequences: A099211 A099212 A099213 * A099215 A099216 A099217

Keyword

easy,nonn

Author

Paul Barry, Oct 06 2004

Status

approved