23181

Appears in sequences

• Numbers k such that the period of the continued fraction for sqrt(k) contains exactly 84 ones.at n=25A031852
• Semiprimes in A054567.at n=23A113692
• Numbers k such that (k!-8)/8 is prime.at n=15A139203
• Wiener index of a benzenoid consisting of a spiral chain of n hexagons (s=1; see the Gutman et al. reference).at n=17A193391
• a(n) = 16*n^2 + 2*n + 1.at n=38A204675
• G.f.: Sum_{n>=0} (x^n - 1)^n * x^n / (1-x)^(n+1).at n=38A243919
• Expansion of Sum_{p prime, i>=2} x^(p^i)/(1 - x^(p^i)) / Product_{j>=1} (1 - x^j).at n=35A281611
• Number of nX4 0..1 arrays with every element unequal to 0, 1, 3, 4, 5 or 7 king-move adjacent elements, with upper left element zero.at n=7A305914
• T(n,k)=Number of nXk 0..1 arrays with every element unequal to 0, 1, 3, 4, 5 or 7 king-move adjacent elements, with upper left element zero.at n=58A305918
• Number of vertices formed by drawing the lines connecting any two of the 2*(n+2) perimeter points of a 3 X (n+1) rectangular grid of points (or equally, a 2 X n grid of squares).at n=17A331763