8473921

Appears in sequences

• Square octagonal numbers.at n=3A036428
• Expansion of 1/((1-x^2)*(1-4*x+x^2)).at n=12A072335
• Expansion of g.f. (2+7*x+2*x^2)/((x^2-1)*(1+4*x+x^2)).at n=13A097947
• Member r=16 of the family of Chebyshev sequences S_r(n) defined in A092184.at n=7A098301
• Octagonal numbers equal to S*(3S - 2) with 3S - 2 = k^2 and S semiprime.at n=22A124106
• Triangle T(n, k, q) = c(n, q)/(c(k, q)*c(n-k, q)), where c(n, q) = Product_{j=1..n} t(2*j, q), t(n, q) = (1/4)*( (2 + sqrt(q))^n + (2 - sqrt(q))^n - 2 ), and q = 3, read by rows.at n=29A173585
• Triangle T(n, k, q) = c(n, q)/(c(k, q)*c(n-k, q)), where c(n, q) = Product_{j=1..n} t(2*j, q), t(n, q) = (1/4)*( (2 + sqrt(q))^n + (2 - sqrt(q))^n - 2 ), and q = 3, read by rows.at n=34A173585
• Number of 2 X n array permutations with each element moving zero or one space horizontally or diagonally.at n=12A189450