OFFSET
1,1
COMMENTS
Conjecture: (1) tau(x)/tau(x-1) = n has solutions for every n. (2) If x is the smallest number for a given n such that tau(x)/tau(x-1) = n > 1, then x-1 is a prime.
LINKS
Jinyuan Wang, Table of n, a(n) for n = 1..10000
EXAMPLE
12 is a member as tau(12)/tau(11) = 3, 15 is a member as tau(15)/tau(14) = 1.
MAPLE
with(numtheory): a:=proc(n) if type(tau(n)/tau(n-1), integer)=true then n else fi end: seq(a(n), n=2..150); # Emeric Deutsch, Mar 25 2005
PROG
(PARI) isok(n) = denominator(numdiv(n)/numdiv(n-1)) == 1; \\ Michel Marcus, Apr 12 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Amarnath Murthy, Aug 28 2003
EXTENSIONS
More terms from David Wasserman and Emeric Deutsch, Mar 25 2005
STATUS
approved