A065901 Duplicate of A053662.
3, 5, 9, 21, 23, 33, 39, 51, 63, 65, 81, 89, 95, 99, 113, 131, 173, 183, 191, 209, 215
Offset: 0
This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
Filtered([1..100], n-> not (Factorial(n)+1) mod (2*n+1)=0) # G. C. Greubel, May 18 2019
[n: n in [1..100] | not (Factorial(n)+1) mod (2*n+1) eq 0 ]; // G. C. Greubel, May 18 2019
Select[Range[100],!Divisible[#!+1,2#+1]&] (* Harvey P. Dale, Sep 09 2014 *)
isok(n) = (n!+1) % (2*n+1) \\ Michel Marcus, Jul 12 2013
[n for n in (1..100) if not Mod(factorial(n)+1, 2*n+1)==0 ] # G. C. Greubel, May 18 2019