27841

Appears in sequences

• Maximal number of regions obtained by joining n points around a circle by straight lines. Also number of regions in 4-space formed by n-1 hyperplanes.at n=29A000127
• Starting positions of strings of three 6's in the decimal expansion of Pi.at n=22A083625
• Maximum number of odd 2 X 2 submatrices over all 2n X 2n (0,1) matrices.at n=10A093699
• Indices of primes in sequence defined by A(0) = 39, A(n) = 10*A(n-1) - 1 for n > 0.at n=19A101847
• Sum of the squares of the first n nonsquarefree numbers (A013929).at n=22A111732
• a(n) = n^3 + (1-n)^2.at n=30A168297
• Positive integers of the form (10*m^2+1)/11.at n=31A179338
• Numbers n such that (n^n-2)/(n-2) is an integer.at n=32A242787
• a(n) = Sum_{1 <= x_1, x_2, x_3 <= n} gcd(x_1, n)/gcd(x_1, x_2, x_3, n).at n=21A373060