OFFSET
0,2
COMMENTS
Diagonal sums of number triangle A003983.
LINKS
Harvey P. Dale, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (2,2,-3,-2,-2,4).
FORMULA
a(n)=sum{k=0..floor(n/2), sum{j=0..n-k, [j<=k]*2^(k-j)[j<=n-2k]2^(n-2k-j)}}.
G.f.: 1/((1-2x)(1-2x^2)(1-x^3)); a(n)=2a(n-1)+2a(n-2)-3a(n-3)-2a(n-4)-2a(n-5)+4a(n-6); - Paul Barry, Jan 18 2006
MATHEMATICA
LinearRecurrence[{2, 2, -3, -2, -2, 4}, {1, 2, 6, 13, 30, 62}, 40] (* Harvey P. Dale, Oct 18 2021 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Paul Barry, Jan 16 2006
STATUS
approved