2222222221

Appears in sequences

• Expansion of g.f. x*(1+10*x)/((1-x)*(1-10*x^2)).at n=19A094623
• Smallest semiprime containing exactly n 2's.at n=8A104669
• Numbers k such that sigma(k) + phi(k) is a repdigit.at n=28A116019
• List of pairs (n,m) with n < m such that the decimal expansion of m is a cyclic shift of that of n and m^2 is a cyclic shift of n^2.at n=27A134514
• Second elements of the pairs listed in A134514.at n=13A134585
• a(n) is the number 2 written (prime(n)-1)/2 times followed by the digit 1; a(1)=2.at n=7A137287
• a(n) = (2*10^n - 11)/9.at n=9A165402
• Expansion of x*(1 + 2*x + 10*x^2)/((1 - x^2)*(1 - 10*x^2)).at n=19A322925