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 A218830 Largest odd integer not of the form p+2q with p, q, p^2+4(2^n-1)q^2 all prime, or 0 if there would be no such upper bound. 0
 3449, 1711, 73, 15, 6227, 1051, 2239, 2599, 7723, 781, 1163, 587, 11443, 2279, 157, 587, 32041, 1051, 2083, 4681 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS This is the sequence M defined in a comment to A218825. Zhi-Wei Sun has conjectured (Nov 07 2012) that for any n>0, there is only a finite number of positive odd integers not of the given form. See arXiv:1211.1588. LINKS Zhi-Wei Sun, Conjectures involving primes and quadratic forms, arxiv:1211.1588 [math.NT], 2012-2017. EXAMPLE The exceptionally low values a(3), a(4) and a(15) correspond to the sets: E(3) = {1,3,5,7,31,73} = { 2n-1: for no prime q, both p=2n-1-2q and p^2+28*q^2 are prime }, E(4) = {1,3,5,7,9,11,13,15} = { 2n-1: A218825(n)=0 }, E(15) = {1,3,5,7,9,13,15,31,33,35,37,73,89,157} = { 2n-1: for no prime q, both p=2n-1-2q and p^2+4(2^15-1)q^2 are prime }. CROSSREFS Cf. A218825, A046927, A000040. Sequence in context: A107537 A260500 A202644 * A210626 A341553 A340437 Adjacent sequences:  A218827 A218828 A218829 * A218831 A218832 A218833 KEYWORD nonn,more AUTHOR Zhi-Wei Sun and M. F. Hasler, Nov 07 2012 STATUS approved

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Last modified May 20 16:05 EDT 2022. Contains 353874 sequences. (Running on oeis4.)