Series for first parallel moment of square lattice.

Terms

a(0) =2a(1) =8a(2) =24a(3) =62a(4) =148a(5) =330a(6) =710a(7) =1464a(8) =2962a(9) =5814a(10) =11288a(11) =21406a(12) =40364a(13) =74570a(14) =137602a(15) =249088a(16) =451868a(17) =804766a(18) =1440580a(19) =2529686a(20) =4482584a(21) =7775166a(22) =13664146a(23) =23446020a(24) =40953840a(25) =69518842a(26) =120978656a(27) =203223692a(28) =352808860a(29) =586473542