Related to the Herschel graph.

Terms

a(0) =1a(1) =3a(2) =25a(3) =243a(4) =2425a(5) =24243a(6) =242425a(7) =2424243a(8) =24242425a(9) =242424243a(10) =2424242425a(11) =24242424243a(12) =242424242425