Growth series for Heisenberg group.

Terms

a(0) =1a(1) =4a(2) =12a(3) =36a(4) =82a(5) =164a(6) =294a(7) =476a(8) =724a(9) =1052a(10) =1464a(11) =1972a(12) =2590a(13) =3324a(14) =4186a(15) =5188a(16) =6336a(17) =7644a(18) =9124a(19) =10780a(20) =12626a(21) =14676a(22) =16934a(23) =19412a(24) =22124a(25) =25076a(26) =28280a(27) =31748a(28) =35486a(29) =39508