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A301894
Number of real lines on a smooth real cubic surface.
0
OFFSET
1,1
COMMENTS
Schläfli proved that a smooth real cubic surface contains either 3, 7, 15, or 27 straight lines.
FORMULA
a(n) = A097080(n) = 2*n^2 - 2*n + 3 for n = 1, 2, 3, 4.
EXAMPLE
The number of lines on a smooth complex cubic surface is a(4) = A027363(2) = A238370(1) = 27.
CROSSREFS
Sequence in context: A051054 A001649 A303220 * A213215 A353578 A324719
KEYWORD
nonn,fini,full
AUTHOR
Jonathan Sondow, Mar 28 2018
STATUS
approved