OFFSET
1,1
COMMENTS
Also composite squarefree numbers n such that (3*p(i)+1) | (3*n-1).
LINKS
Giovanni Resta, Table of n, a(n) for n = 1..77 (terms < 2*10^12)
EXAMPLE
The prime factors of 773227 are 7, 13, 29 and 293. We see that (773227 - 1/3)/(7 + 1/3) = 231968, (773227 - 1/3)/(13 + 1/3) = 57992, (773227 - 1/3)/(29 + 1/3) = 26360 and (773227 - 1/3)/(293 + 1/3) = 2636. Hence 773227 is in the sequence.
The prime factors of 1128387 are 3, 13 and 28933. We see that
(1128387 - 1/3)/(3 + 1/3) = 338516, (1128387 - 1/3)/(13 + 1/3) = 84629 but (1128387 - 1/3)/(28933 + 1/3) = 84629/2170. Hence 1128387 is not in the sequence.
MAPLE
CROSSREFS
KEYWORD
nonn,hard
AUTHOR
Paolo P. Lava, May 29 2013
EXTENSIONS
a(5)-a(22) from Giovanni Resta, Jun 02 2013
STATUS
approved