71425670400domain: NAppears in sequencesOne third of triple factorial numbers.at n=9A034001Expansion of e.g.f. x*(1+x-3*x^2)/(1-3*x).at n=10A052690a(n) = (n+1)*a(n-3), a(0)=a(1)=a(2)=1 for n>1.at n=29A081406