Number of ordered triples (w,x,y) with all terms in {-n,...,0,...,n} and w + x + y = 2.

Terms

a(0) =0a(1) =3a(2) =15a(3) =33a(4) =57a(5) =87a(6) =123a(7) =165a(8) =213a(9) =267a(10) =327a(11) =393a(12) =465a(13) =543a(14) =627a(15) =717a(16) =813a(17) =915a(18) =1023a(19) =1137a(20) =1257a(21) =1383a(22) =1515a(23) =1653a(24) =1797a(25) =1947a(26) =2103a(27) =2265a(28) =2433a(29) =2607