OFFSET
1,2
COMMENTS
Numbers n such that A236747(n) = 0.
Probably finite. Perhaps a(4565) = 2591107 is the last term; any other terms are greater than 10^9. - Charles R Greathouse IV, Feb 03 2014
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 1..4565
MATHEMATICA
nkQ[n_]:=!PrimeQ[n]&&Count[PrimeQ/@Table[n+{k, -k}, {k, Floor[Sqrt[n]]}], _?(# == {True, True}&)]==0; Select[Range[250], nkQ] (* Harvey P. Dale, Jun 08 2022 *)
PROG
(PARI) is(n)=for(k=0, sqrtint(n), if(isprime(n-k)&&isprime(n+k), return(0))); 1 \\ Charles R Greathouse IV, Feb 03 2014
CROSSREFS
KEYWORD
nonn
AUTHOR
Juri-Stepan Gerasimov, Feb 01 2014
STATUS
approved