OFFSET
1,2
COMMENTS
It is conjectured that the density decreases. In each century the number of members are so far: 41, 30, 26, 28, 23, 24, 24, 21, 24, 22, ...
MATHEMATICA
Select[ Range[178], Mod[ Sum[ HarmonicNumber[k] k! (# - k)!, {k, 1, #}], # + 1] != 0 &] (* Robert G. Wilson v, Jan 14 2004; corrected by Jean-François Alcover, May 22 2014 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Leroy Quet, Jan 08 2004
EXTENSIONS
Extended by Robert G. Wilson v, Jan 14 2004
STATUS
approved