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 A078496 Smallest prime p such that p>n and 2*n-p is also prime. 12
 5, 7, 7, 11, 11, 11, 13, 17, 13, 19, 17, 17, 19, 23, 19, 31, 23, 23, 31, 29, 29, 31, 29, 31, 37, 41, 31, 43, 41, 37, 37, 41, 41, 43, 47, 41, 43, 53, 43, 67, 47, 47, 61, 53, 53, 61, 53, 59, 61, 59, 61, 67, 59, 61, 73, 71, 61, 79, 71, 67, 67, 71, 71, 73, 83, 71, 73, 83, 73, 79 (list; graph; refs; listen; history; text; internal format)
 OFFSET 4,1 COMMENTS Suggested by Goldbach Conjecture. Values of q from A143697. This follows from the factorization n^2-k^2 = (n-k)(n+k). LINKS P. CAMI, Table of n, a(n) for n = 4..60000 FORMULA n>3 integer; a(n)=min{p: p>n; p, 2*n-p are primes}. EXAMPLE a(11)=17. MATHEMATICA Table[p=n+1; q=2n-p; While[q>0&&!(PrimeQ[p]&&PrimeQ[q]), p++; q-- ]; p, {n, 4, 100}] PROG (PARI) a(n) = {my(p=nextprime(n+1)); while(!isprime(2*n-p), p = nextprime(p+1)); p; } \\ Michel Marcus, Oct 22 2016 CROSSREFS Cf. A143697, A078587. a(n) = 2n - A078587(n) Cf. A082467 Sequence in context: A201459 A053672 A087525 * A114521 A258653 A159482 Adjacent sequences:  A078493 A078494 A078495 * A078497 A078498 A078499 KEYWORD nonn AUTHOR Serhat Sevki Dincer (sevki(AT)ug.bilkent.edu.tr), Nov 26 2002 EXTENSIONS Edited by N. J. A. Sloane, Jan 24 2009 at the suggestion of R. J. Mathar and T. D. Noe. STATUS approved

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Last modified December 7 13:08 EST 2021. Contains 349581 sequences. (Running on oeis4.)