OFFSET
1,2
EXAMPLE
A177151 = (1,2,2,2,3,4,4,5,5,6,7,7,8,9,9,10,10,11,12,12,...), so that singletons occur in positions (1,5,10,13,18,...).
CROSSREFS
KEYWORD
nonn,changed
AUTHOR
Clark Kimberling, May 03 2010
STATUS
approved