1329410domain: NAppears in sequencesa(n) is the number m such that f(sqrt(n)) is in the field Q(sqrt(m)), where f(x) is defined from the continued fraction x = [c(0),c(1),...] as [c(0)+2, c(1)+2,...].at n=28A229958Numbers k of the form p^2 + 1 (for prime p) where k^2 + 1 is also prime.at n=26A235053