Series for second perpendicular moment of hexagonal lattice.

Terms

a(0) =2a(1) =12a(2) =46a(3) =144a(4) =402a(5) =1040a(6) =2548a(7) =5992a(8) =13632a(9) =30220a(10) =65486a(11) =139404a(12) =291770a(13) =602908a(14) =1229242a(15) =2482792a(16) =4959014a(17) =9836840a(18) =19323246a(19) =37773464a(20) =73182570a(21) =141345292a(22) =270647584a(23) =517513972a(24) =980893354