OFFSET
1,1
COMMENTS
This sequence is not well-defined for many reasons (negative years are ill-defined; calendars change often, so when does a year begin?; what does "observed" mean?; what if the comet was observed both at the end of one year and at the beginning of another, as in 1985/1986?; etc.). - N. J. A. Sloane, Jun 24 2007
LINKS
Joseph M. Laufer, Halley's Comet, Its 30th Recorded Return, 1985-1986.
EXAMPLE
a(30) = 1985 because the 30th recorded appearance of Halley's comet was in 1985.
CROSSREFS
KEYWORD
sign
AUTHOR
David Terr, Jan 03 2005
STATUS
approved