3280256domain: NAppears in sequencesOctagonal numbers equal to S*(3S - 2) with 3S - 2 = k^2 and S semiprime.at n=17A124106Octagonal numbers of the form C*(3C - 2) with 3C - 2 = k^2 and C a composite number.at n=26A125511Cyclops octagonal numbers: a(n) = n*(3*n-2) with one "zero" digit in the middle.at n=28A285767