OFFSET
1,2
COMMENTS
A063994(a(n)) = 1. - Reinhard Zumkeller, Mar 02 2013
a(n) = A111305(n-2) for n >= 3. - Emmanuel Vantieghem, Jul 03 2013
All terms except the first one are even. Missing even terms are A039772. - Robert G. Wilson v, Sep 26 2016
Numbers n such that A187730(n) = 1. - Thomas Ordowski, Dec 29 2016
LINKS
Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
MAPLE
select(n -> igcd(n-1, numtheory:-phi(n)) = 1, [$1..1000]); # Robert Israel, Nov 09 2015
MATHEMATICA
Select[Range[200], GCD[# - 1, EulerPhi[#]] == 1 &]
PROG
(Haskell)
a209211 n = a209211_list !! (n-1)
a209211_list = filter (\x -> (x - 1) `gcd` a000010 x == 1) [1..]
-- Reinhard Zumkeller, Mar 02 2013
(PARI) isok(n) = gcd(n-1, eulerphi(n)) == 1; \\ Michel Marcus, Sep 26 2016
CROSSREFS
KEYWORD
nonn
AUTHOR
José María Grau Ribas, Mar 06 2012
STATUS
approved