OFFSET
0,2
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..400
FORMULA
G.f.: (1-x)^2/(x*Q(0)) + 1 - 1/x, where Q(k)= 1 - x - x*(k+1)/Q(k+1); (continued fraction). - Sergei N. Gladkovskii, May 18 2013
G.f.: T(0)*(1-x)/x + 1 - 1/x, where T(k) = 1 - x*(k+1)/( x*(k+1) - (1-x)^2/T(k+1) ); (continued fraction). - Sergei N. Gladkovskii, Nov 26 2013
From G. C. Greubel, Sep 28 2023: (Start)
a(n) = ( ((2*n-1)*(4*n^2 - 4*n + 5))*a(n-1) + (4*n^2 + 3)*a(n-2) )/(4*n^2 - 8*n + 7), with a(0) = 1, a(1) = 4.
E.g.f.: (-1 + 4*x + 2*(1-x)*sqrt(1-2*x))*exp(1-sqrt(1-2*x))/(sqrt(1-2*x))^3. (End)
MAPLE
MATHEMATICA
Join[{1}, Differences[RecurrenceTable[{a[0]==1, a[1]==2, a[n]== (2n-1)a[n-1]+ a[n-2]}, a[n], {n, 25}], 2]] (* Harvey P. Dale, Jun 18 2011 *)
PROG
(Magma) [n le 2 select 4^(n-1) else ( ((2*n-3)*(4*n^2-12*n+13))*Self(n-1) + (4*n^2-8*n+7)*Self(n-2) )/(4*n^2-16*n+19): n in [1..30]]; // G. C. Greubel, Sep 28 2023
(SageMath)
def A144647_list(prec):
P.<x> = PowerSeriesRing(QQ, prec)
return P( (-1+4*x+2*(1-x)*sqrt(1-2*x))*exp(1-sqrt(1-2*x))/(sqrt(1-2*x))^3 ).egf_to_ogf().list()
A144647_list(40) # G. C. Greubel, Sep 28 2023
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Jan 26 2009
EXTENSIONS
More terms from R. J. Mathar, Feb 01 2009
STATUS
approved