222221

Appears in sequences

• Rotating digits of a(n)^2 right once still yields a square.at n=23A045877
• Expansion of g.f. x*(1+10*x)/((1-x)*(1-10*x^2)).at n=11A094623
• Near-repdigit semiprimes with 2 as repeated digit.at n=26A105983
• Numbers k such that sigma(k) + phi(k) is a repdigit.at n=17A116019
• 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=11A134514
• Second elements of the pairs listed in A134514.at n=5A134585
• a(n) = 1 + 111110*n.at n=2A135403
• a(n) is the number 2 written (prime(n)-1)/2 times followed by the digit 1; a(1)=2.at n=4A137287
• a(n) = (2*10^n - 11)/9.at n=5A165402
• Shortest (x+1,2x)-code of n.at n=32A233135
• For k in {2,3,...,9} define a sequence as follows: a(0)=0; for n>=0, a(n+1)=a(n)+1, unless a(n) ends in k, in which case a(n+1) is obtained by replacing the last digit of a(n) with the digit(s) of k^2. This is k(4).at n=46A237341
• Non-repdigit numbers n such that A045876(n) ends with n.at n=4A276802
• Expansion of x*(1 + 2*x + 10*x^2)/((1 - x^2)*(1 - 10*x^2)).at n=11A322925
• List of co-Lyndon words on {1,2} sorted first by length and then lexicographically.at n=22A329318
• Numbers k that are the representation of primes in base 3 and in base 4.at n=28A340290