42517

Appears in sequences

• Numbers k such that the continued fraction for sqrt(k) has odd period and if the last term of the periodic part is deleted the two central terms are both 45.at n=4A031633
• Largest proper divisor of the n-th Carmichael number (A002997).at n=34A081703
• Number of walks within N^3 (the first octant of Z^3) starting at (0,0,0) and consisting of n steps taken from {(-1, -1, 0), (-1, 0, 0), (1, -1, 0), (1, -1, 1), (1, 1, 0)}.at n=9A149540
• a(n) = n*(2*n^2 + 5*n + 19)/2.at n=34A163675
• Denominators of r-Egyptian fraction expansion for Pi - 3, where r = (1,1/4,1/9,1/16,...).at n=3A270377
• Expansion of e.g.f. (tan x + sec x)^2*(E.g.f. for A000738).at n=7A292761
• a(n) = Sum_{k = 1..n} ( n/gcd(k, n) )^4.at n=9A372965