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A264526 Smallest number m such that both 2*n-m and 2*n+m are primes.

%I A264526 #24 Nov 16 2024 18:49:05
%S A264526 1,1,3,3,1,3,3,1,3,9,5,3,9,1,9,3,5,9,3,1,3,15,5,3,9,7,3,15,1,9,3,5,15,
%T A264526 3,1,15,3,5,9,15,5,3,9,7,9,15,7,9,3,1,3,3,1,3,15,13,15,9,7,9,15,13,21,
%U A264526 21,5,3,27,1,9,15,5,33,9,1,15,3,7,9,3,5
%N A264526 Smallest number m such that both 2*n-m and 2*n+m are primes.
%H A264526 Reinhard Zumkeller, <a href="/A264526/b264526.txt">Table of n, a(n) for n = 2..10000</a>
%F A264526 a(n) = A260689(n,1);
%F A264526 a(A040040(n)) = 1;
%F A264526 a(A014574(n)/2) = 1;
%F A264526 a(A088763(n)) = 3.
%F A264526 a(n) = A082467(2n). - _Ivan N. Ianakiev_, Oct 27 2021
%t A264526 snm[n_]:=Module[{m=1},While[!PrimeQ[2n-m]||!PrimeQ[2n+m],m=m+2];m]; Array[ snm,90,2] (* _Harvey P. Dale_, Aug 13 2017, optimized by _Ivan N. Ianakiev_, Mar 16 2018 *)
%o A264526 (Haskell)
%o A264526 a264526 = head . a260689_row
%o A264526 (PARI) a(n) = {my(m=1); while(!(isprime(2*n-m) && isprime(2*n+m)), m+=2); m;} \\ _Michel Marcus_, Mar 18 2018
%Y A264526 Cf. A014574, A040040, A082467, A088763, A260689, A264527.
%K A264526 nonn
%O A264526 2,3
%A A264526 _Reinhard Zumkeller_, Nov 17 2015