A327470 Maximum valency of the central line in a certain smooth 2D-polarized K3-surface in P^{n+1}.

12, 9, 8, 7, 6, 5, 5, 5, 5, 5, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4

Offset

2,1

Links

Table of n, a(n) for n=2..85.

Alex Degtyarev, Lines on smooth polarized K3-surfaces, arXiv:1706.05734 [math.AG], 2017; Discrete & Computational Geometry 62.3 (2019): 601-648, DOI:10.1007/s00454-018-0038-5. Prop. 2.10.

Prog

(Python)
def a(n): return 4 if n > 11 else 5 if n > 6 else 12-n if n > 2 else 12
print([a(n) for n in range(2, 50)]) # Michael S. Branicky, Dec 09 2021

Crossrefs

Sequence in context: A326927 A338289 A018870 * A379665 A068614 A163920

Adjacent sequences: A327467 A327468 A327469 * A327471 A327472 A327473

Keyword

nonn

Author

N. J. A. Sloane, Oct 03 2019

Extensions

a(8)-a(11) edited to match Proposition 2.12, p. 11, of Degtyarev link. - Michael S. Branicky, Dec 09 2021

Status

approved