a(n) = n*7^n.

Terms

a(0) =0a(1) =7a(2) =98a(3) =1029a(4) =9604a(5) =84035a(6) =705894a(7) =5764801a(8) =46118408a(9) =363182463a(10) =2824752490a(11) =21750594173a(12) =166095446412