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A064123 Number of divisors of 5^n - 1 that are relatively prime to 5^m - 1 for all 0 < m < n. 1
3, 2, 2, 2, 4, 2, 2, 2, 4, 2, 2, 2, 2, 4, 4, 4, 4, 2, 8, 4, 4, 8, 4, 2, 16, 4, 16, 2, 8, 4, 4, 4, 4, 4, 16, 4, 8, 8, 4, 4, 4, 8, 4, 4, 8, 4, 2, 2, 2, 4, 8, 4, 8, 8, 16, 2, 2, 4, 4, 4, 8, 8, 8, 8, 8, 4, 32, 16, 16, 4, 4, 8, 8, 8, 32, 4, 8, 4, 8, 4, 4, 16, 8, 4, 8, 16, 8, 2, 64, 2, 4, 2, 8, 8, 16, 4, 8, 8 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Harry J. Smith, Table of n, a(n) for n = 1..119

Sam Wagstaff, Cunningham Project, Factorizations of 5^n-1, n odd, n<376

MATHEMATICA

a = {1}; Do[ d = Divisors[ 5^n - 1 ]; l = Length[ d ]; c = 0; k = 1; While[ k < l + 1, If[ Union[ GCD[ a, d[ [ k ] ] ] ] == {1}, c++ ]; k++ ]; Print[ c ]; a = Union[ Flatten[ Append[ a, Transpose[ FactorInteger[ 5^n - 1 ] ][ [ 1 ] ] ] ] ], {n, 1, 58} ]

PROG

(PARI) { allocatemem(932245000); for (n=1, 119, d=divisors(5^n - 1); l=length(d); a=0; for (i=1, l, t=1; for (m=1, n - 1, p=5^m - 1; if (gcd(d[i], p)!=1, t=0; break)); if (t, a++)); write("b064123.txt", n, " ", a) ) } \\ Harry J. Smith, Sep 08 2009

CROSSREFS

Cf. A063982.

Sequence in context: A106267 A096101 A104890 * A024703 A102845 A064126

Adjacent sequences:  A064120 A064121 A064122 * A064124 A064125 A064126

KEYWORD

nonn

AUTHOR

Robert G. Wilson v, Sep 10 2001

EXTENSIONS

More terms from Harry J. Smith, Sep 08 2009

STATUS

approved

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Last modified November 27 05:55 EST 2021. Contains 349363 sequences. (Running on oeis4.)