191807

Appears in sequences

• Lucas-Carmichael numbers: squarefree composite numbers k such that p | k => p+1 | k+1.at n=33A006972
• Lucas-Carmichael numbers with 4 prime factors.at n=10A216926
• Least Lucas-Carmichael number whose Dedekind psi value is an n-th power.at n=4A292573
• a(n) is the smallest k such that tau(k^2 + 1) is equal to 2^n, where tau = A000005 and a(n) = -1 if no such k exists.at n=8A380969