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A247216 Maximum of the smallest prime factors of (i^prime(n)-1)/(i-1), when i runs through all integers in [2, prime(n)]. 2
3, 13, 31, 55987, 12207031, 16148168401, 50544702849929377, 109912203092239643840221, 11111111111111111111111, 7369130657357778596659, 568972471024107865287021434301977158534824481, 388230138454493 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

If in the definition "maximum" is replaced with "minimum," then we obtain A035095 (see comment there).

LINKS

Table of n, a(n) for n=1..12.

FORMULA

a(n) == 1 (mod prime(n)).

MAPLE

with(numtheory):

a:= n-> max(seq(min(factorset(

        (i^ithprime(n)-1)/(i-1))[]), i=2..ithprime(n))):

seq(a(n), n=1..10);  # Alois P. Heinz, Dec 06 2014

MATHEMATICA

a[n_] := Max[Table[Min[FactorInteger[(i^Prime[n]-1)/(i-1)][[All, 1]]], {i, 2, Prime[n]}]];

Table[a[n], {n, 1, 12}] (* Jean-Fran├žois Alcover, Mar 25 2017, after Alois P. Heinz *)

CROSSREFS

Cf. A020639, A035095.

Sequence in context: A128067 A052493 A279068 * A301926 A211800 A218922

Adjacent sequences:  A247213 A247214 A247215 * A247217 A247218 A247219

KEYWORD

nonn

AUTHOR

Vladimir Shevelev, Nov 26 2014

EXTENSIONS

More terms from Peter J. C. Moses, Nov 26 2014

STATUS

approved

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Last modified May 31 22:35 EDT 2020. Contains 334756 sequences. (Running on oeis4.)