Series for first parallel moment of hexagonal lattice.

Terms

a(0) =0a(1) =4a(2) =24a(3) =104a(4) =384a(5) =1284a(6) =4012a(7) =11924a(8) =34100a(9) =94584a(10) =255852a(11) =677850a(12) =1764482a(13) =4523924a(14) =11447870a(15) =28636218a(16) =70907326a(17) =173991368a(18) =423469988a(19) =1023162920a(20) =2455645268a(21) =5858183260a(22) =13898041838a(23) =32804047708a(24) =77067740230