A144672
Numbers x,y,z such that UnitarySigma(x) = UnitarySigma(y) = UnitarySigma(z) = 3*(x*y*z)^(1/2)/(- x^(1/2) + 8*y^(1/2) - 5*z^(1/2)), z<=y<=x; sequence gives x.
Original entry on oeis.org
2, 20, 24, 360, 816, 1056, 12240, 15840, 29120, 181632, 337977, 2724480, 93358848, 1400382720
Offset: 1
Factorization of a(11) : 17*3^2*47^2.
A144674
Numbers x,y,z such that UnitarySigma(x) = UnitarySigma(y) = UnitarySigma(z) = 3*(x*y*z)^(1/2)/(- x^(1/2) + 8*y^(1/2) - 5*z^(1/2)), z<=y<=x; sequence gives z.
Original entry on oeis.org
2, 20, 24, 360, 816, 1056, 12240, 15840, 29120, 181632, 287300, 2724480, 93358848, 1400382720
Offset: 1
Factorization of a(11) : 17*5^2*2^2*13^2.
A145680
a(n) = smallest number m such that UnitarySigma(m) = nm/(n-1).
Original entry on oeis.org
6, 2, 3, 4, 5, 216, 7, 8, 9, 5292000, 11, 10584000, 13, 4991499040640000, 165375, 16, 17, 235270656, 19, 101867327360000, 8107610881081625211441398582431641600000, 19235716742537891017605454376709022095843377283072000000, 23, 552063590295800832, 25
Offset: 2
UnitarySigma(216) = 2^2*3^2*7 = (7/6)*216.
A145681
Numbers m such that A034448(m) = 3m/2, where A034448 = unitary sigma = sum of divisors d with gcd(d,m/d)=1.
Original entry on oeis.org
2, 20, 24, 360, 816, 1056, 12240, 15840, 29120, 181632, 2724480, 9192960, 13790400, 15288000, 93358848, 199180800, 1130734080, 1400382720, 25115166720, 544161945600, 3089165506560, 11519246340096, 172788695101440, 274358081249280, 5944425093734400, 33746043993661440, 7425442423511040000, 25976914334122752000000, 48787315395486187520000, 56897897650906642513920
Offset: 1
Showing 1-4 of 4 results.
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