OFFSET
4,2
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R. Austin, R. K. Guy, and R. Nowakowski, unpublished notes, circa 1987.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 = 4..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R. Austin, R. K. Guy, and R. Nowakowski, Unpublished notes, 1987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-4)! * Stirling2(n+2, n-3). - Alois P. Heinz, Apr 27 2022
MAPLE
a:= n-> Stirling2(2+n, n-3)*(n-4)!:
seq(a(n), n=4..21); # Alois P. Heinz, Apr 27 2022
MATHEMATICA
Table[(n-4)!*StirlingS2[n+2, n-3], {n, 4, 35}] (* G. C. Greubel, Nov 22 2022 *)
PROG
(Magma) [Factorial(n-4)*StirlingSecond(n+2, n-3): n in [4..35]]; // G. C. Greubel, Nov 22 2022
(SageMath) [factorial(n-4)*stirling_number2(n+2, n-3) for n in range(4, 36)] # G. C. Greubel, Nov 22 2022
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
More terms from Alois P. Heinz, Apr 27 2022
STATUS
approved