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A049586 a(n) is the GCD of the cototients (A051953) of n and n+1. 6
1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 5, 3, 1, 1, 1, 1, 3, 3, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 5, 1, 1, 1, 1, 3, 3, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 3, 3, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 3 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,9
COMMENTS
Most of the terms are 1.
LINKS
FORMULA
a(n) = gcd(n + 1 - phi(n+1), n - phi(n)).
a(n) = gcd(A051953(n+1), A051953(n)).
MATHEMATICA
Map[GCD @@ Map[# - EulerPhi@ # &, #] &, Partition[Range@ 106, 2, 1]] (* Michael De Vlieger, Aug 09 2017 *)
PROG
(Magma) [GCD((n+1-EulerPhi(n+1)), n-EulerPhi(n)): n in [1..100]]; // Vincenzo Librandi, Aug 10 2017
CROSSREFS
Sequence in context: A070670 A368472 A368711 * A342466 A133721 A083202
KEYWORD
nonn
AUTHOR
Labos Elemer, Dec 28 2000
STATUS
approved

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Last modified February 25 13:12 EST 2024. Contains 370330 sequences. (Running on oeis4.)