A170930 G(n,1) with n index G(n,i)=n*(G(n,i-1)+G(n,i-2))=(a^i-b^i)*d where d=sqrt(n*(n+4)); a=(n+d)/2; b=(n-d)/2

0, 21, 63, 252, 945, 3591, 13608, 51597, 195615, 741636, 2811753, 10660167, 40415760, 153227781, 580930623, 2202475212, 8350217505, 31658078151, 120024886968, 455048895357, 1725221346975, 6540810726996, 24798096221913

Offset

0,2

Comments

n=1 A022088 n=2 12*A002605 n=3 above n=4 ... new

Links

Table of n, a(n) for n=0..22.

Formula

a(n) = 3*a(n-1)+3*a(n-2) = 21*A030195(n). G.f.: 21*x/(1-3*x-3*x^2). [From R. J. Mathar, Feb 05 2010]

Example

G(n,0)=0 G(n,1)=n*(n+4)

Crossrefs

see above

Sequence in context: A025525 A033850 A251213 * A113622 A069215 A115921

Adjacent sequences: A170927 A170928 A170929 * A170931 A170932 A170933

Keyword

nonn

Author

Claudio Peruzzi (claudio.peruzzi(AT)gmail.com), Feb 04 2010

Extensions

More terms from R. J. Mathar, Feb 05 2010

Status

approved