196049701domain: NAppears in sequencesStrong pseudoprimes to base 2 and 5.at n=22A215568Triangular numbers (A000217) that are also centered pentagonal numbers (A005891).at n=7A254628Numbers k such that both k and 2k-1 are Poulet numbers (Fermat pseudoprimes to base 2).at n=5A298758