524975domain: NAppears in sequencesNumbers k such that phi(5k-1) = sigma(k).at n=6A067224Numbers k such that k*(k+1) gives the concatenation of two numbers m and m+1.at n=7A116294Least positive integer m such that m*n divides F(m+n), where F(k) denotes the k-th Fibonacci number A000045(k).at n=24A297573