OFFSET
1,1
LINKS
Steve Humble, Create your own mathematical mysteries, +plus magazine, University of Cambridge.
EXAMPLE
6=2*3 and 1/2 + 2/3 + 3/6 - 4/6 = 1, so 6 belongs to the sequence.
PROG
(PARI) isok(n) = f = factor(n)[, 1]; 1/f[1] + sum(i=2, #f, f[i-1]/f[i]) + f[#f]/n - (#f~ + 2)/n == 1;
CROSSREFS
KEYWORD
nonn
AUTHOR
Michel Marcus, May 26 2014
STATUS
approved