Series for second perpendicular moment of hexagonal lattice.

Terms

a(0) =0a(1) =2a(2) =12a(3) =54a(4) =206a(5) =712a(6) =2294a(7) =7024a(8) =20656a(9) =58842a(10) =163250a(11) =443062a(12) =1180156a(13) =3092964a(14) =7993116a(15) =20401250a(16) =51502616a(17) =128748512a(18) =319010540a(19) =784179992a(20) =1913668608a(21) =4639155964a(22) =11178566462a(23) =26784974870a(24) =63851541584