OFFSET
1,3
COMMENTS
There are only 11 0 values for n<434, and no more 0 values for n>433.
If n>433, a(n) is > A200652.
LINKS
Pierre CAMI, Table of n, a(n) for n = 1..10000
MAPLE
A200653 := proc(n)
for k from 2*n-1 to -2 by -1 do
if isprime(n*(n+1)+k) and isprime(n*(n+1)+k+2) then
return k;
end if;
end do:
return 0 ;
end proc:
seq(A200653(n), n=1..80) ; # R. J. Mathar, Nov 22 2011
MATHEMATICA
a[n_]:=Module[{k=0}, For[m=-2, m<2n, m++, If[PrimeQ[n(n+1)+m]&&PrimeQ[n(n+1)+m+2], k=m]]; k]; Array[a, 66] (* Stefano Spezia, Apr 01 2024 *)
CROSSREFS
KEYWORD
sign
AUTHOR
Pierre CAMI, Nov 20 2011
STATUS
approved