172451

Appears in sequences

• Numbers n such that pi(n) = prime(d_1)*prime(d_2)*...*prime(d_k) where d_1 d_2 ... d_k is the decimal expansion of n.at n=4A098683
• Numbers n such that pi(n) = prime(d_1)*prime(d_2)* ... *prime(d_k), where d_1, d_2, ... d_k is the decimal expansion of n, and the zeroth prime is 1.at n=8A160040
• G.f.: Sum_{n>=0} x^n / (1+x)^(2*n+1) * [Sum_{k=0..n} C(n,k)^2 * x^k] * [Sum_{k=0..n} C(n,k)^2 * (-x)^k].at n=7A249891