%N Complete list of numbers of twisted cubics on a general Calabi-Yau threefold which is a complete intersection in some projective space.
%C There are exactly five types of such threefolds: the quintic in P^4, the complete intersections (3, 3) and (2, 4) in P^5, the complete intersection (2, 2, 3) in P^6 and finally (2, 2, 2, 2) in P^7. The counts are listed in that order.
%H Geir Ellingsrud and Stein Arild Stromme, <a href="http://arxiv.org/abs/alg-geom/9411005">Bott's formula and enumerative geometry</a>, J. Amer. Math. Soc. 9 (1996), 175-193; arXiv:alg-geom/9411005, 1994. See Th. 1.1.
%A _N. J. A. Sloane_, Jan 22 2020