OFFSET
0,2
LINKS
Robert Israel, Table of n, a(n) for n = 0..1545
FORMULA
G.f.: ((1+x-sqrt(1-2*x-11*x^2)))/(2*x). - Michael Somos, Jun 08 2000; corrected by Robert Israel, Sep 10 2020
a(n) = (3/(11*n)) * ((3+n)*A025237(n+1) - (2*n+3)*A025237(n)) for n>0. [Mark van Hoeij, Jul 02 2010]
(n+1)*a(n) = (2*n-1)*a(n-1)+11*(n-2)*a(n-2). - Robert Israel, Sep 10 2020
G.f.: 1 + 3*x/(1 - x - 3*x^2/(1 - x - 3*x^2/(1 - x - 3*x^2/(1 - x - 3*x^2/(1 - ...))))) (continued fraction). - Nikolaos Pantelidis, Nov 24 2022
MAPLE
seq(coeff(convert(series((1+x-sqrt(1-2*x-11*x^2))/(2*x), x, 50), polynom), x, i), i=0..30);
MATHEMATICA
Rest[CoefficientList[Series[(1+x-Sqrt[1-2x-11x^2])/2, {x, 0, 30}], x]] (* Harvey P. Dale, Apr 17 2019 *)
PROG
(PARI) a(n)=polcoeff((1+x-sqrt(1-2*x-11*x^2+x*O(x^n)))/2, n)
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
Corrected by C. Ronaldo (aga_new_ac(AT)hotmail.com) and Ralf Stephan, Dec 19 2004
STATUS
approved