Series for first parallel moment of hexagonal lattice.

Terms

a(0) =0a(1) =4a(2) =20a(3) =68a(4) =196a(5) =512a(6) =1256a(7) =2936a(8) =6628a(9) =14528a(10) =31140a(11) =65414a(12) =135276a(13) =275656a(14) =555216a(15) =1105726a(16) =2182380a(17) =4268906a(18) =8290740a(19) =15984420a(20) =30638312a(21) =58369924a(22) =110665328a(23) =208734268a(24) =392103508a(25) =733311754a(26) =1366650536a(27) =2537201920