OFFSET
1,1
LINKS
Andrew Howroyd, Table of n, a(n) for n = 1..10000
EXAMPLE
The sequence of all dividing pairs (columns) begins:
1 1 2 1 1 2 1 3 1 1 1 2 1 4 2 1 1 3 1 1 1 2 1 1
1 2 2 3 4 4 5 3 6 7 8 6 9 4 8 10 11 6 12 13 14 10 15 16
MATHEMATICA
Select[Range[100], And[PrimeOmega[#]==2, Or[PrimePowerQ[#], Divisible@@Reverse[PrimePi/@FactorInteger[#][[All, 1]]]]]&]
PROG
(PARI) ok(n)={my(f=factor(n)); bigomega(f)==2 && (#f~==1 || primepi(f[2, 1]) % primepi(f[1, 1]) == 0)} \\ Andrew Howroyd, Oct 26 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, Sep 06 2018
STATUS
approved