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A285711 a(n) = gcd(A051953(n), A079277(n)), a(1) = 1. 5
1, 1, 1, 2, 1, 4, 1, 4, 3, 2, 1, 1, 1, 8, 1, 8, 1, 4, 1, 4, 9, 4, 1, 2, 5, 2, 9, 16, 1, 1, 1, 16, 1, 2, 1, 8, 1, 4, 3, 8, 1, 6, 1, 8, 3, 8, 1, 4, 7, 10, 1, 4, 1, 12, 5, 1, 3, 2, 1, 2, 1, 32, 1, 32, 1, 2, 1, 4, 1, 2, 1, 16, 1, 2, 5, 8, 1, 18, 1, 16, 27, 2, 1, 3, 1, 4, 1, 16, 1, 3, 1, 16, 3, 16, 1, 1, 1, 8, 3, 20, 1, 2, 1, 8, 3, 2, 1, 24, 1, 10, 3, 2, 1, 6, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..10000

FORMULA

a(1) = 1; for n > 1, a(n) = gcd(A051953(n), A079277(n)).

MATHEMATICA

Table[GCD[n - EulerPhi@ n, If[n <= 2, 1, Module[{k = n - 2, e = Floor@ Log2@ n}, While[PowerMod[n, e, k] != 0, k--]; k]]], {n, 115}] (* Michael De Vlieger, Apr 26 2017 *)

PROG

(Scheme) (define (A285711 n) (if (= 1 n) n (gcd (A051953 n) (A079277 n))))

(Python)

from sympy import divisors, totient, gcd

from sympy.ntheory.factor_ import core

def a007947(n): return max(list(filter(lambda i: core(i) == i, divisors(n))))

def a079277(n):

    k=n - 1

    while True:

        if a007947(k*n) == a007947(n): return k

        else: k-=1

def a(n): return 1 if n==1 else gcd(n - totient(n), a079277(n))

print [a(n) for n in xrange(1, 151)] # Indranil Ghosh, Apr 26 2017

CROSSREFS

Cf. A009195, A051953, A079277, A285707, A285709, A285710.

Sequence in context: A229340 A322968 A072721 * A035092 A160598 A107457

Adjacent sequences:  A285708 A285709 A285710 * A285712 A285713 A285714

KEYWORD

nonn

AUTHOR

Antti Karttunen, Apr 26 2017

STATUS

approved

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Last modified September 20 01:58 EDT 2019. Contains 327207 sequences. (Running on oeis4.)