A171116 - OEIS

%I #8 May 02 2022 17:27:46

%S 0,0,0,105,109781,12597900,302280963,3356773532,23599355991,

%T 122416062018,510681301550,1807308075111,5622246678741,15761274284852,

%U 40547443860105,97044388890450,218379097055159,465931135430250,948922558475388,1854955331788517,3496355565562725

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

%H Sergey Fomin and Grigory Mikhalkin, <a href="https://doi.org/10.4171/JEMS/238">Labeled floor diagrams for plane curves</a>, Journal of the European Mathematical Society 012.6 (2010): 1453-1496; arXiv:<a href="https://arxiv.org/abs/0906.3828">0906.3828</a> [math.AG], 2009-2010.

%H <a href="/index/Rec#order_13">Index entries for linear recurrences with constant coefficients</a>, signature (13,-78,286,-715,1287,-1716,1716,-1287,715,-286,78,-13,1).

%t a[n_ ? (#<4&)] = 0;

%t 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;

%t Table[a[n], {n, 20}] (* _Andrey Zabolotskiy_, May 02 2022 *)

%Y Cf. A171108.

%K nonn,easy

%O 1,4

%A _N. J. A. Sloane_, Sep 27 2010

%E Name edited, terms a(7) and beyond added by _Andrey Zabolotskiy_, May 02 2022