Series for second parallel moment of hexagonal lattice.

Terms

a(0) =0a(1) =6a(2) =60a(3) =314a(4) =1240a(5) =4166a(6) =12600a(7) =35324a(8) =93576a(9) =236944a(10) =578764a(11) =1371478a(12) =3169380a(13) =7165478a(14) =15901324a(15) =34705018a(16) =74661832a(17) =158529158a(18) =332756408a(19) =691084378a(20) =1421836528a(21) =2899678894a(22) =5867341452a(23) =11784640984a(24) =23512608484