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- #!/usr/bin/ruby
- # Numbers that are not powers of primes (A024619) whose harmonic mean of their proper unitary divisors is an integer.
- # https://oeis.org/A335270
- # Conjecture: all terms have the form n*(usigma(n)-1) where usigma(n)-1 is prime.
- for k in (1..1e9) {
- var p = k.usigma.dec
- p.is_prime || next
- var m = (k * p)
- var o = m.omega
- o > 1 || next
- if (m.usigma.dec `divides` m*o.ipow2.dec) {
- say [k, m]
- }
- }
- __END__
- [12, 228]
- [35, 1645]
- [75, 7725]
- [231, 88473]
- [108558, 20295895122]
- [120620, 22550994580]
|
