21241

Appears in sequences

• Numbers k such that the period of the continued fraction for sqrt(k) contains exactly 100 ones.at n=9A031868
• Denominators of continued fraction convergents to sqrt(703).at n=7A042353
• Numbers k such that k + sigma(k) + sigma(sigma(k)) is a square.at n=40A116014
• Centered 12-gonal numbers which are semiprimes, intersection of A003154 and A001358.at n=24A218172
• a(n) = prime(n)^n mod n^n.at n=5A262207