51381

Appears in sequences

• Numbers k such that 2^(k-1) + k is prime.at n=5A061422
• a(1)=1; a(n) = Sum_{1<=k<n, gcd(k,n(n+1)/2)=1} a(k).at n=27A125597
• Number of equivalence classes of 132-avoiding permutations of [n], where two permutations are equivalent if they have the same set of pure descents.at n=13A295704