OFFSET
1,1
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..200
FORMULA
G.f.: (1-sqrt(1-12*x+28*x^2))/2. - Michael Somos, Jun 08 2000
n*a(n) = (12*n-18)*a(n-1)-28*(n-3)*a(n-2). - Richard Choulet, Dec 16 2009
a(n) ~ sqrt(3*sqrt(2)-2) * (2*(3+sqrt(2)))^n / (2*sqrt(14*Pi)*n^(3/2)). - Vaclav Kotesovec, Oct 11 2013
MATHEMATICA
Rest[CoefficientList[Series[(1-Sqrt[1-12*x+28*x^2])/2, {x, 0, 20}], x]] (* Vaclav Kotesovec, Oct 11 2013 *)
nxt[{n_, a_, b_, c_}]:={n+1, b, c, (c(12n-6)-28(n-2)*b)/(n+1)}; NestList[ nxt, {3, 3, 2, 12}, 20][[All, 2]] (* Harvey P. Dale, Jun 04 2019 *)
PROG
(PARI) a(n)=polcoeff((1-sqrt(1-12*x+28*x^2+x*O(x^n)))/2, n)
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved