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

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, 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, 21, 5, 3, 27, 1, 9, 15, 5, 33, 9, 1, 15, 3, 7, 9, 3, 5

Offset

2,3

Links

Reinhard Zumkeller, Table of n, a(n) for n = 2..10000

Formula

a(n) = A260689(n,1);

a(A040040(n)) = 1;

a(A014574(n)/2 = 1;

a(A088763(n)) = 3.

a(n) = A082467(2n). - Ivan N. Ianakiev, Oct 27 2021

Mathematica

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 *)

Prog

(Haskell)
a264526 = head . a260689_row
(PARI) a(n) = {my(m=1); while(!(isprime(2*n-m) && isprime(2*n+m)), m+=2); m; } \\ Michel Marcus, Mar 18 2018

Crossrefs

Cf. A014574, A040040, A082467, A088763, A260689, A264527.

Sequence in context: A169609 A353527 A220670 * A138071 A206400 A321129

Adjacent sequences: A264523 A264524 A264525 * A264527 A264528 A264529

Keyword

nonn

Author

Reinhard Zumkeller, Nov 17 2015

Status

approved