"Virtual" number of rational curves (or rather, stable maps) of degree n in P^3 which meet 2n+1 general lines and are Legendrian, i.e., are tangent to the standard contact distribution in P^3.

A328553

"Virtual" number of rational curves (or rather, stable maps) of degree n in P^3 which meet 2n+1 general lines and are Legendrian, i.e., are tangent to the standard contact distribution in P^3.