153270

Appears in sequences

• Integers y such that for some integer x we have uphi(x) = uphi(y) = x-y, where uphi(n) = A047994(n) is the unitary totient function: If n = Product p_i^e_i, uphi(n) = Product (p_i^e_i - 1).at n=20A067741
• Triangle read by rows: T(n,k) is the number of secondary structures of size n having k stacks of length 2 (n>=0, k>=0).at n=44A202841
• Averages y of twin prime pairs that satisfy y = x^2 + x - 2.at n=23A214840
• Numbers k for which phi(A267099(k)) is equal to phi(k), but the number of 4m+1 and 4m+3 primes in the prime factorization of k (when counted with multiplicity) is not equal. Here A267099 is fully multiplicative involution swapping the positions of 4m+1 and 4m+3 primes, and phi is Euler totient function.at n=11A354194