OFFSET
0,2
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..375
FORMULA
From G. C. Greubel, Sep 23 2018: (Start)
a(n) = 27^n * Hermite(n, 2/27).
E.g.f.: exp(4*x - 729*x^2).
a(n) = numerator(Sum_{k=0..floor(n/2)} (-1)^k*n!*(4/27)^(n-2*k)/(k!*(n-2*k)!)). (End)
EXAMPLE
Numerators of 1, 4/27, -1442/729, -17432/19683, 6237580/531441...
MATHEMATICA
Numerator[HermiteH[Range[0, 20], 2/27]] (* Harvey P. Dale, Mar 26 2016 *)
Table[27^n*HermiteH[n, 2/27], {n, 0, 30}] (* G. C. Greubel, Sep 23 2018 *)
PROG
(PARI) a(n)=numerator(polhermite(n, 2/27)) \\ Charles R Greathouse IV, Jan 29 2016
(PARI) x='x+O('x^30); Vec(serlaplace(exp(4*x - 729*x^2))) \\ G. C. Greubel, Sep 23 2018
(Magma) [Numerator((&+[(-1)^k*Factorial(n)*(4/27)^(n-2*k)/( Factorial(k) *Factorial(n-2*k)): k in [0..Floor(n/2)]])): n in [0..30]]; // G. C. Greubel, Sep 23 2018
CROSSREFS
KEYWORD
sign,frac
AUTHOR
N. J. A. Sloane, Nov 12 2009
STATUS
approved