Semiperimeter of the n-th Heronian triangle.

Terms

a(0) =3a(1) =6a(2) =21a(3) =78a(4) =291a(5) =1086a(6) =4053a(7) =15126a(8) =56451a(9) =210678a(10) =786261a(11) =2934366a(12) =10951203a(13) =40870446a(14) =152530581a(15) =569251878a(16) =2124476931a(17) =7928655846a(18) =29590146453a(19) =110431929966a(20) =412137573411