2621440

Appears in sequences

• a(n) = (n+2)*2^(n-1).at n=18A001792
• a(n) = 10*4^n.at n=9A002066
• a(n) = n*4^(n-1).at n=10A002697
• a(n) = lcm(n, 2^(n-1)).at n=19A014964
• a(n) = 5 * 2^n.at n=19A020714
• Numbers of form 8^i*10^j, with i, j >= 0.at n=29A025634
• a(n) = Sum_{k=0..floor(n/2)} k*binomial(n,2*k) = floor(n*2^(n-3)).at n=20A049610
• Integer part of denominators of nonzero terms in asymptotic expansion of the Riemann-Seigel Z-function.at n=21A050277
• Nonprimes n such that n+cototient(n) is a power of 2.at n=36A053162
• a(n) = (9*2^n + (-2)^n)/4 for n>0.at n=19A056486
• Numbers k such that k = 2*phi(k) + phi(phi(k)).at n=36A063920
• 20-almost primes (generalization of semiprimes).at n=3A069281
• Numbers of the form 5*2^n or 5*3*2^n; a(n) = 5*A029744(n).at n=37A070004
• Binary expansion is 1x100...0 where x = 0 or 1.at n=38A070875
• a(1)=2, a(n+1) = 2*a(n) - phi(a(n)) where phi is the Euler totient function A000010.at n=31A072944
• a(n) = the least positive integer k satisfying Omega(k) = Omega(k-1)+...+Omega(k-n) if such k exists; = 0 otherwise. (Omega(n) (A001222) denotes the number of prime factors of n, counting multiplicity.)at n=6A076183
• Numbers k such that phi(k) is a perfect tenth power.at n=21A078170
• Refactorable numbers x, such that quotient x/A000005(x) equals a power of 2.at n=20A078541
• Expansion of g.f.: (1+x^2)/(1-2*x).at n=21A084215
• Sum of the integer elements in the subsets of the subsets of the integers 1 to n.at n=5A087085