72120

Appears in sequences

• Numbers k such that 7*10^k + 5*R_k - 2 is prime, where R_k = 11...1 is the repunit (A002275) of length k.at n=12A103061
• Number T(n,k) of permutations of [n] with exactly k (possibly overlapping) occurrences of the consecutive step patterns 010 or 101, where 1=up and 0=down; triangle T(n,k), n >= 0, k = max(0, n-3), read by rows.at n=27A295987