A171116 a(n) is the Severi degree for curves of degree n and cogenus 6.

0, 0, 0, 105, 109781, 12597900, 302280963, 3356773532, 23599355991, 122416062018, 510681301550, 1807308075111, 5622246678741, 15761274284852, 40547443860105, 97044388890450, 218379097055159, 465931135430250, 948922558475388, 1854955331788517, 3496355565562725

Offset: 1

Author

N. J. A. Sloane, Sep 27 2010

Keywords

• nonn
• easy

Links

• Sergey Fomin and Grigory Mikhalkin, Labeled floor diagrams for plane curves, Journal of the European Mathematical Society 012.6 (2010): 1453-1496; arXiv:0906.3828 [math.AG], 2009-2010.
• Index entries for linear recurrences with constant coefficients, signature (13,-78,286,-715,1287,-1716,1716,-1287,715,-286,78,-13,1).

Crossrefs

Cf. A171108.

Programs

Mathematica

a[n_ ? (#<4&)] = 0;
a[n_] := 81/80 n^12 - 243/20 n^11 - 81/20 n^10 + 8667/16 n^9 - 9297/8 n^8 - 47727/5 n^7 + 2458629/80 n^6 + 3243249/40 n^5 - 6577679/20 n^4 - 25387481/80 n^3 + 6352577/4 n^2 + 8290623/20 n - 2699706;
Table[a[n], {n, 20}] (* Andrey Zabolotskiy, May 02 2022 *)

Extensions

Name edited, terms a(7) and beyond added by Andrey Zabolotskiy, May 02 2022