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A264526 Smallest number m such that both 2*n-m and 2*n+m are primes. 5
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 (list; graph; refs; listen; history; text; internal format)
OFFSET
2,3
LINKS
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
Sequence in context: A169609 A353527 A220670 * A138071 A206400 A321129
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Nov 17 2015
STATUS
approved

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Last modified May 20 02:53 EDT 2024. Contains 372703 sequences. (Running on oeis4.)