69648

Appears in sequences

• a(1) = 1, a(2n) = 16a(n), a(2n+1) = a(2n)+1.at n=26A033052
• a(n) = n^4 + n^3 + n.at n=16A100606
• a(n) = 121*n^2 - 2*n.at n=23A157040
• a(n) = gpf(a(n-3))*gpf(a(n-2)) + gpf(a(n-1)), with a(1)=a(2)=1 and a(3)=2 and where gpf(n) is the greatest prime dividing n, A006530(n).at n=18A258804
• Expansion of phi(-q^6) / phi(-q) in powers of q where phi() is a Ramanujan theta function.at n=30A262968
• Nonunitary doubly superperfect numbers: numbers k such that nusigma(nusigma(k)) = 2*k, where nusigma(k) = sigma(k) - usigma(k) is the sum of nonunitary divisors of k (A048146).at n=3A329881