691186

Appears in sequences

• Numbers k such that the continued fraction for sqrt(k) has odd period and if the last term of the periodic part is deleted the two central terms are both 66.at n=21A031654
• Number of different strings of length n obtained from "abcd" by iteratively duplicating any substring.at n=16A137744
• Indices of centered heptagonal numbers (A069099) that are also octagonal numbers (A000567).at n=9A254856