42585

Appears in sequences

• Number of 3 X 3 integer matrices with elements in the range [ -n,n ] which represent a rotation of order 2.at n=16A053171
• Odd composite numbers k such that cototient(k) - phi(k) = k - 2*phi(k) is an odd prime.at n=12A083255
• L-matrix for Euler numbers A000111(n+1).at n=37A147315
• Triangle read by rows: T(n,k) is the number of permutations of {1,2,...,n} having k up-down runs (1 <= k <= n).at n=43A186370
• Antidiagonal sums of the convolution array A213833.at n=16A213834
• a(n) = -2^n*(E(n, 1/2) + E(n, 1) + (n mod 2)*2*(E(n+1, 1/2) + E(n+1, 1))), where E(n, x) are the Euler polynomials.at n=9A240559
• a(n) = -2^(2*n+1)*(E(2*n+1, 1/2) + E(2*n+1, 1) + 2*(E(2*n+2, 1/2) + E(2*n+2, 1))), where E(n,x) are the Euler polynomials.at n=4A241242
• a(1) = 0, a(2) = 1, and for n > 2, a(n) = 2*a(A252463(n)) + [n == 1 (mod 4)].at n=52A292385
• Numbers x that are equal to lpf(x)*gpf(x)*(lpf(x)+gpf(x))/2, where lpf(x) < gpf(x) are the least and the greatest prime factors of x: A020639 and A006530.at n=38A307108