OFFSET
1,1
COMMENTS
Terms can be written as (4xy +- (x-y)) - 1 for x > 0, y > 0. - Ron R Spencer, Aug 01 2016
Numbers k such that (4*k)!/(4*k + 3) is an integer. - Peter Bala, Jan 25 2017
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..1000
FORMULA
a(n) = (A091236(n) - 3)/4.
EXAMPLE
Distribution of the positive terms in the following triangular array:
*;
3, *;
*, 8, *;
6, *, 15, *;
*, 13, *, 24, *;
9, *, 22, *, 35, *;
*, 18, *, 33, *, 48, *;
etc., where * marks the noninteger values of (2*h*k + k + h-1)/2 with h >= k >= 1. - Vincenzo Librandi, Apr 22 2014
MAPLE
for n from 0 to 100 do
if irem(factorial(4*n), 4*n+3) = 0 then print(n); end if;
end do: # Peter Bala, Jan 25 2017
MATHEMATICA
Select[Range[150], !PrimeQ[4#+3]&] (* Harvey P. Dale, Jul 04 2011 *)
PROG
(Magma) [n: n in [0..110] |not IsPrime(4*n+3)]; // Vincenzo Librandi, Apr 22 2014\
(PARI) is(n)=!isprime(4*n+3) \\ Charles R Greathouse IV, Aug 01 2016
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Antti Karttunen, Jun 01 2004
STATUS
approved