154289

Appears in sequences

• G.f.: A(x) = 1 + x*A(x)*A(-x) + x^2*exp( Sum_{n>=1} 2*L(n)^2*x^(2*n)/n ), where A(x) = exp(Sum_{n>=1} L(n)*x^n/n).at n=31A205566
• Smallest i such that prime(n) divides gcd(sigma(i), phi(i)) (cf. A009223).at n=33A222714
• Numbers of the form p*q, p and q prime with q=2*p+3.at n=28A226754
• Solution of the complementary equation a(n) = a(n-1) + a(n-2) + b(n-1) + b(n-2) - n, where a(0) = 1, a(1) = 3, b(0) = 2, b(1) = 4.at n=21A294417
• Number of Lyndon compositions of n where every pair of adjacent parts (including the last with the first) is relatively prime.at n=23A328669