202525domain: NAppears in sequencesNumbers k such that k | 4^k + 1.at n=20A015950Numbers k that divide 4^k + 1, k not a power of 5.at n=12A015974Numbers k such that the least term in the periodic part of the continued fraction for sqrt(k) is 36.at n=24A031714a(n) = 625*n^2 + 25.at n=17A157915