110246

Appears in sequences

• Number of permutations p of {1,...,n} such that exactly one element of {p(1),...,p(i-1)} is between p(i) and p(i+1) for all i from 2 to n-1.at n=21A185030
• Sum_{k=1..n} (-1)^isprime(k)*2^k.at n=15A242002