OFFSET
1,2
REFERENCES
P. Blasiak, K. A. Penson and A. I. Solomon, The general boson normal ordering problem, Phys. Lett. A 309 (2003) 198-205.
M. Schork, On the combinatorics of normal ordering bosonic operators and deforming it, J. Phys. A 36 (2003) 4651-4665.
FORMULA
MATHEMATICA
a[n_] := Sum[Product[FactorialPower[k+6*(j-1), 2], {j, 1, n}]/k!, {k, 2, Infinity}]/E; Array[a, 11] (* Jean-François Alcover, Sep 01 2016 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Wolfdieter Lang, Feb 27 2004
STATUS
approved