589818

Appears in sequences

• Start with a single triangle; at n-th generation add a triangle at each vertex, allowing triangles to overlap; sequence gives number of triangles in n-th generation.at n=33A061776
• a(n) = 9*2^n - 6.at n=16A089143
• Coefficients of 1/(Sum_{k>=0} [(k+1)*r]*(-x)^k), where r = sqrt(7/3) and [ ] = floor.at n=19A288135