cp's OEIS Frontend

A065377 Primes not of the form p + k^2, with p prime and k > 0.

%I A065377 #22 Mar 03 2020 06:57:18
%S A065377 2,5,13,31,37,61,127,379,439,571,829,991,1549,3319,7549
%N A065377 Primes not of the form p + k^2, with p prime and k > 0.
%C A065377 Probably finite and 7549 is the last entry. - _Robert G. Wilson v_, Nov 05 2001
%C A065377 No more terms below 10^9. - _Mauro Fiorentini_, Mar 02 2020
%p A065377 N:= 10^6: # to get all entries <= N
%p A065377 Primes:= select(isprime,{2,seq(2*i+1,i=1..floor((N-1)/2))}):
%p A065377 A:= NULL:
%p A065377 for i from 1 to nops(Primes) do
%p A065377 for k from floor(sqrt(Primes[i])) to 1 by -1 do
%p A065377    if isprime(Primes[i] - k^2) then break fi
%p A065377 od:
%p A065377 if k = 0 then A:= A, Primes[i] fi;
%p A065377 od:
%p A065377 A; # _Robert Israel_, Sep 03 2014
%t A065377 Do[ k = 1; p = Prime[n]; While[k^2 < p && !PrimeQ[p - k^2], k++ ]; If[k^2 > p, Print[p]], {n, 1, 10^6} ]
%t A065377 Module[{nn=1000,pr},pr=Flatten[Table[Prime[n]+Range[nn]^2,{n,nn}]];Complement[Prime[Range[nn]],pr]] (* _Harvey P. Dale_, May 30 2014 *)
%o A065377 (PARI) is(p)=forstep(m=2,sqrtint(p),2,if(isprime(p-m^2),return(0)));isprime(p) && (p==2 || !issquare(p-2)) \\ _Charles R Greathouse IV_, Jun 04 2012
%Y A065377 Cf. A000040. Complement of A065376.
%K A065377 nonn
%O A065377 1,1
%A A065377 _Reinhard Zumkeller_, Nov 03 2001
%E A065377 Offset corrected by _Charles R Greathouse IV_, May 29 2012