Series for second parallel moment of hexagonal lattice.

Terms

a(0) =0a(1) =6a(2) =68a(3) =442a(4) =2218a(5) =9528a(6) =36834a(7) =131856a(8) =445000a(9) =1433294a(10) =4444006a(11) =13349510a(12) =39041224a(13) =111583236a(14) =312618368a(15) =860662498a(16) =2333112020a(17) =6238124024a(18) =16474149036a(19) =43023953304a(20) =111230237224a(21) =284926172100a(22) =723731637254