OFFSET
1,2
COMMENTS
Theorem: a(1) = 1, a(2) = 6; thereafter, a(n) is the smallest nonprime squarefree number m not yet in the sequence such that
(i) gcd(m, a(n-1)) > 1,
(ii) gcd(m, a(n-2)) = 1, and
(iii) m does not divide a(n-1).
Conjecture: The sequence is a permutation of A000469.
LINKS
Scott R. Shannon, Table of n, a(n) for n = 1..100000
Scott R. Shannon, White on black graph of first 50000 terms [The green line is x = y]
Scott R. Shannon, Image of the first 500000 terms in color. The terms with a lowest prime factor of 2,3,5,7,9,11,13,17,19,>=23 are colored white, red, orange, yellow, green, blue, indigo, violet, gray respectively.
Rémy Sigrist, PARI program
PROG
(PARI) See Links section.
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved