122313

Appears in sequences

• Numbers that end with decimal digit 1, 3, 7, or 9 and that produce only composite numbers when any of the digits 0,1,...,9 is inserted anywhere in them (including at the beginning or end).at n=3A125268
• a(n) = Sum_{k=0..n} 3^(n-k) * binomial(n,k) * binomial(n+3,k).at n=6A388410