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A367004
a(n) is the smallest prime factor of n*2^n+1.
5
3, 3, 5, 5, 7, 5, 3, 3, 11, 7, 13, 13, 3, 3, 17, 17, 5, 11, 3, 3, 23, 13, 5, 5, 3, 3, 7, 29, 31, 17, 3, 3, 47, 19, 37, 37, 3, 3, 41, 41, 13, 23, 3, 3, 11, 5, 7, 7, 3, 3, 53, 7, 5591, 29, 3, 3, 5, 31, 37, 61, 3, 3, 5, 5, 67, 5, 3, 3, 7, 37, 11, 41, 3, 3, 149
OFFSET
1,1
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..914 (terms 1..350 from Robert Israel)
FORMULA
a(n) = A020639(A002064(n)).
MAPLE
seq(min(numtheory:-factorset(n*2^n+1)), n=1..100); # Robert Israel, Nov 09 2023
MATHEMATICA
Table[FactorInteger[n 2^n+1][[1, 1]], {n, 80}] (* Harvey P. Dale, Aug 14 2024 *)
KEYWORD
nonn,changed
AUTHOR
Sean A. Irvine, Oct 31 2023
STATUS
approved