Series for second perpendicular moment of square lattice (eventually changes sign).

Terms

a(0) =0a(1) =2a(2) =8a(3) =24a(4) =64a(5) =156a(6) =358a(7) =786a(8) =1664a(9) =3434a(10) =6902a(11) =13656a(12) =26464a(13) =50772a(14) =95754a(15) =179442a(16) =331294a(17) =609496a(18) =1106106a(19) =2004852a(20) =3586874a(21) =6423028a(22) =11351274a(23) =20126538a(24) =35191190a(25) =61883196a(26) =107179834a(27) =187216848a(28) =321395596a(29) =558468104