137137

Appears in sequences

• Double primes: concatenation of the n-th prime with itself.at n=32A176597
• Number of ordered set partitions of the multiset [a,a,1,1,...,1] with two "a" and n "1".at n=26A209633
• E.g.f.: Sum_{n>=0} d^n/dx^n (x + x^2)^(2*n) / (2*n)!.at n=7A215125
• a(n) = Sum_{k=0..floor(n/3)} (n-k)!/(k! * (n-3*k)!).at n=14A358560