205408

Appears in sequences

• a(n) = (1/3)*(n^2 + 2*n + 3)*(n+1)^2.at n=27A014820
• Octagonal numbers equal to S*(3S - 2) with 3S - 2 = k^2 and S semiprime.at n=11A124106
• Octagonal numbers of the form C*(3C - 2) with 3C - 2 = k^2 and C a composite number.at n=13A125511