30421

Appears in sequences

• a(n) = n-th centered n-gonal number.at n=39A100119
• Expansion of 1/(1-x*(1-6*x)).at n=13A145934
• a(n) = 20*n^2 + 1.at n=39A158493
• Number of 8-step S, E, and NW-moving king's tours on an n X n board summed over all starting positions.at n=9A187513
• Semiprimes of the form 5*n^2 + 1.at n=26A212707
• Integers x such that [f(0), f(f(0)), ..., f(...f(0)...)] is a permutation of [0, 1, ..., k-1], where k is the number of digits in x and f(a) denotes the 0-based index of the first occurrence of the substring a in x.at n=23A307620
• Number of squarefree integers with an odd number of prime factors <= 10^n.at n=5A348708
• Expansion of A(x) satisfying -x = Sum_{n=-oo..+oo} (-x)^n * (1 - (-x)^n)^n / A(x)^n.at n=12A363139
• a(n) = Sum_{1 <= x_1, x_2, x_3 <= n} ( gcd(x_1, n)/gcd(x_1, x_2, x_3, n) )^2.at n=12A371492