66469

Appears in sequences

• a(n) = (1/12)*(n+1)*(n^3+19*n^2+118*n+228).at n=26A092327
• Numbers k such that 5*10^k + R_k + 2 is a prime, where R_k = 11...1 is the repunit (A002275) of length k.at n=15A103005
• a(n) = least k such that 3^k mod k = 2^n.at n=16A128148
• G.f.: Product_{i>=1, j>=1} 1/(1 - x^(i*j))^(i*j).at n=14A280540
• Odd numbers k > 1 such that k == 1 (mod 4), Product_{n>=1} (a(n)-1)/(a(n)+1) = Pi/4, and Limit_{n->oo} a(n+1)/a(n) = 3, where a(1) = 13 (see comments).at n=8A317986
• Semiprimes with only semiprime digits, each appearing at least once.at n=32A349275