26860680

Appears in sequences

• a(n) = 4*(n+1)*binomial(n+2,8).at n=14A027781
• a(n) = 15*(n+1)*binomial(n+2,15)/2.at n=7A027788
• Smallest x such that sigma(x) = n*phi(x), or -1 if no such x exists.at n=24A055234
• a(n) = Min {x : sigma(x) = phi(n*x), x is not a prime}, least nonprime solutions to sigma(x) = phi(n*x).at n=24A087979
• a(n) = Min{x : sigma(x) = n*phi(x), x is not a prime}, the least nonprime solutions to sigma(x) = n*phi(x); special balanced numbers.at n=24A088830
• a(n) = numerator of r(n), where r(n) = (4*n+2)!/((3*n)!*2^n).at n=5A227624
• a(n) is the least number k > 0 such that sigma(k) = phi(n*k).at n=24A256527
• Balanced numbers (A020492) k with a record value of sigma(k)/phi(k).at n=13A335287