132020domain: NAppears in sequencesa(n) = n*(n+1)*(4*n+1)/2.at n=40A135713Numbers whose k digits can be permuted into a new k-digit number according to rules explained in the Comments section.at n=18A330418G.f. A(x) satisfies A(x^3) = A(x)^3/(1 + 3*A(x)).at n=34A386659