Number of lines through at least two points of a centered hexagonal grid of size n.

Terms

a(0) =0a(1) =15a(2) =84a(3) =312a(4) =852a(5) =1878a(6) =3654a(7) =6546a(8) =10680a(9) =16668a(10) =25002a(11) =35910a(12) =50136a(13) =68190a(14) =90462a(15) =118200a(16) =152274a(17) =192828a(18) =240480a(19) =296880a(20) =361962a(21) =437832a(22) =525756a(23) =625440a(24) =739146a(25) =867864a(26) =1011822a(27) =1174062a(28) =1354572a(29) =1554114