A171107 a(n) = n*A171106(n).

1, 2, 21, 552, 27385, 2205840, 262793181, 43462178816, 9531675497457, 2677576265015040, 937689127821286885, 400556244184058840064, 205018515960316713766761, 123868925489567035630641152, 87231398219233211815174239405, 70827813121227086927005549854720, 65683870009665683776967740707164641

Offset

1,2

Links

Gheorghe Coserea, Table of n, a(n) for n = 1..222

Sergey Fomin and Grigory Mikhalkin, Labeled floor diagrams for plane curves, arXiv:0906.3828 [math.AG], 2009-2010.

Formula

Sergey Fomin and Grigory Mikhalkin give a recurrence.

Mathematica

terms = 17; Clear[b]; b[1] = b[2] = 1;
y[x_] = Sum[d^2 b[d] x^d/(2 d)!, {d, 1, terms+1}];
f = x (4 y'[x] - E^y[x] - x E^y[x] y'[x]) - 2 y[x] + O[x]^(terms + 1);
Solve[0 == Thread[CoefficientList[f, x]]][[1]] /. Rule -> Set;
a[n_] := n b[n];
Array[a, terms] (* Jean-François Alcover, Dec 14 2018 *)

Crossrefs

Cf. A171106.

Sequence in context: A158886 A092957 A356481 * A218768 A195736 A320653

Adjacent sequences: A171104 A171105 A171106 * A171108 A171109 A171110

Keyword

nonn

Author

N. J. A. Sloane, Sep 27 2010

Extensions

Terms a(15) and beyond from Gheorghe Coserea, Jan 02 2018

Status

approved