29338domain: NAppears in sequencesa(n) = smallest k such that k! ends in 2^n, not counting the trailing zeros.at n=23A058885a(n) = (6*n^4 + 30*n^3 - 20*n^2 + 14)*n/30 + (n mod 2).at n=10A064837Numbers k such that 6*10^k + 17 is prime.at n=21A285632a(n) = Sum_{k=1..n} sigma_2(k) * floor(n/k).at n=38A356042