OFFSET
1,2
COMMENTS
From Artur Jasinski: (Start)
The maximal value of the squarefree kernel of a*b*9^k for every number 9^k and every a,b such that a + b = 9^k and gcd(a,b,3)=1 is never less than 3*(9^k - 1)/4 and is exactly equal to 3*(9^k - 1)/4 for exponents k in this sequence.
Conjecture: This sequence is infinite. (End)
PROG
(PARI) rad(n) = factorback(factor(n)[, 1]); \\ A007947
isok(k) = rad(9^k*(9^k - 1)) == 3*(9^k - 1)/4; \\ Michel Marcus, Dec 24 2022
CROSSREFS
KEYWORD
nonn,hard
AUTHOR
Artur Jasinski, Jan 29 2010
EXTENSIONS
Edited by Jon E. Schoenfield, Dec 23 2022
More terms from Sean A. Irvine, Jun 15 2024
STATUS
approved