OFFSET
5,2
REFERENCES
R. Austin, R. K. Guy, and R. Nowakowski, unpublished notes, circa 1987.
R. K. Guy, personal communication.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
LINKS
G. C. Greubel, Table of n, a(n) for n = 5..440
R. Austin, R. K. Guy, and R. Nowakowski, Unpublished notes, 1987
Milan Janjic, Enumerative Formulas for Some Functions on Finite Sets
Rajesh Kumar Mohapatra and Tzung-Pei Hong, On the Number of Finite Fuzzy Subsets with Analysis of Integer Sequences, Mathematics (2022) Vol. 10, No. 7, 1161.
FORMULA
Essentially Stirling numbers of second kind - see A028246.
a(n) = (n-5)! * Stirling2(n+2, n-4). - G. C. Greubel, Nov 22 2022
MAPLE
seq((d+2)!*(63*d^5-945*d^4+5355*d^3-13951*d^2+15806*d-5304)/2903040, d=5..30) ; # R. J. Mathar, Mar 19 2018
MATHEMATICA
Table[(n-5)!*StirlingS2[n+2, n-4], {n, 5, 35}] (* G. C. Greubel, Nov 22 2022 *)
PROG
(Magma) [Factorial(n-5)*StirlingSecond(n+2, n-4): n in [5..35]]; // G. C. Greubel, Nov 22 2022
(SageMath) [factorial(n-5)*stirling_number2(n+2, n-4) for n in range(5, 36)] # G. C. Greubel, Nov 22 2022
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
STATUS
approved