2211169

Appears in sequences

• Numbers k that require four iterations of the sigma function to be >= 2*k.at n=25A107914
• Squares nearest to and > terms in A098562.at n=4A140597
• Squares n^2 that become prime after omitting all ones in their decimal expansion.at n=23A175983
• Odd numbers N for which numerator(sigma(N)/N) is a prime.at n=40A193065
• Perfect squares which can be written neither as a^2+b^2, nor as a^2+2*b^2, nor as a^2+3*b^2, nor as a^2+7*b^2, with a > 0 and b > 0.at n=15A216408
• Numbers k such that tau(sigma(tau(k))) = sigma(tau(sigma(k))), where tau is A000005 and sigma is A000203.at n=35A237613