OFFSET
21,2
COMMENTS
In this sequence there are no primes. - Artur Jasinski, Dec 02 2007
LINKS
T. D. Noe, Table of n, a(n) for n = 21..1000
Milan Janjic, Two Enumerative Functions.
Index entries for linear recurrences with constant coefficients, signature (22, -231, 1540, -7315, 26334, -74613, 170544, -319770, 497420, -646646, 705432, -646646, 497420, -319770, 170544, -74613, 26334, -7315, 1540, -231, 22, -1).
FORMULA
a(n) = n*(n+1)*(n+2)*(n+3)*(n+4)*(n+5)*(n+6)*(n+7)*(n+8)*(n+9)*(n+10)*(n+11)*(n+12)*(n+13)*(n+14)*(n+15)*(n+16)*(n+17)*(n+18)*(n+19)*(n+20) / 21!. - Artur Jasinski, Dec 02 2007
a(n) = n/(n-21) * a(n-1), n > 21. - Vincenzo Librandi, Mar 26 2011
From Amiram Eldar, Dec 11 2020: (Start)
Sum_{n>=21} 1/a(n) = 21/20.
MAPLE
seq(binomial(n, 21), n=21..41); # Zerinvary Lajos, Aug 04 2008
MATHEMATICA
Table[Binomial[n, 21], {n, 21, 50}] (* Vladimir Joseph Stephan Orlovsky, Apr 22 2011 *)
PROG
(Magma) [ Binomial(n, 21): n in [21..80]]; // Vincenzo Librandi, Mar 26 2011
(PARI) for(n=21, 50, print1(binomial(n, 21), ", ")) \\ G. C. Greubel, Nov 23 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved