OFFSET
0,1
COMMENTS
a(n) = 3 if n is odd. a(n) = 5 if n == 2 (mod 4). - Robert Israel, Nov 20 2023
LINKS
Max Alekseyev, Table of n, a(n) for n = 0..16383
FORMULA
a(n) = A002586(3*n) for n >= 1. - Robert Israel, Nov 20 2023
MAPLE
P1000:= mul(ithprime(i), i= 4..1000):
f:= proc(n) local t;
if n::odd then return 3 elif n mod 4 = 2 then return 5 fi;
t:= igcd(8^n+1, P1000);
if t <> 1 then min(numtheory:-factorset(t)) else min(numtheory:-factorset(8^n+1)) fi
end proc:
map(f, [$0..100]); # Robert Israel, Nov 20 2023
MATHEMATICA
Table[FactorInteger[8^n + 1][[1, 1]], {n, 0, 78}] (* Paul F. Marrero Romero, Oct 20 2023 *)
PROG
(Python)
from sympy import primefactors
def A366671(n): return min(primefactors((1<<3*n)+1)) # Chai Wah Wu, Oct 16 2023
CROSSREFS
KEYWORD
nonn
AUTHOR
Sean A. Irvine, Oct 15 2023
STATUS
approved