141594

Appears in sequences

• Numbers k such that 5*R_k - 2 is prime, where R_k = 11...1 is the repunit (A002275) of length k.at n=12A099416
• The number of reversible primes (palindromic or emirps) by increasing permissible leading digit and by length.at n=28A220344
• Number of emirps of length ceiling(n/4)+1 and leading digit 1, 3, 7 or 9 (in sequence).at n=24A220349