OFFSET
1,2
LINKS
G. C. Greubel, Table of n, a(n) for n = 1..10000
MATHEMATICA
Select[Range[100], !Divisible[#!+1, 2#+1]&] (* Harvey P. Dale, Sep 09 2014 *)
PROG
(PARI) isok(n) = (n!+1) % (2*n+1) \\ Michel Marcus, Jul 12 2013
(Magma) [n: n in [1..100] | not (Factorial(n)+1) mod (2*n+1) eq 0 ]; // G. C. Greubel, May 18 2019
(Sage) [n for n in (1..100) if not Mod(factorial(n)+1, 2*n+1)==0 ] # G. C. Greubel, May 18 2019
(GAP) Filtered([1..100], n-> not (Factorial(n)+1) mod (2*n+1)=0) # G. C. Greubel, May 18 2019
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Chris K. Caldwell, Feb 16 2000
EXTENSIONS
Data corrected by Michel Marcus, Jul 12 2013
STATUS
approved