1449507domain: NAppears in sequencesa(1)=1, a(n) = n*23^(n-1) + a(n-1).at n=4A0149411+2n+3n^2+4n^3+5n^4.at n=23A056579Place n points in general position on each side of an equilateral triangle, and join every pair of the 3*n+3 boundary points by a chord; sequence gives number of vertices in the resulting planar graph.at n=28A367117