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

Terms

a(0) =2a(1) =16a(2) =72a(3) =252a(4) =764a(5) =2094a(6) =5362a(7) =12968a(8) =30138a(9) =67446a(10) =147048a(11) =311940a(12) =649860a(13) =1325234a(14) =2668130a(15) =5278066a(16) =10346200a(17) =19977010a(18) =38329556a(19) =72546986a(20) =136785444a(21) =254596418a(22) =473093498a(23) =868060738a(24) =1593517724