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A083847
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a(n) = number of primes of the form x^2 + 1 <= 2^n.
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6
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1, 1, 2, 2, 3, 4, 5, 6, 8, 10, 12, 14, 18, 24, 33, 42, 54, 70, 91, 114, 158, 212, 293, 393, 539, 713, 957, 1301, 1792, 2459, 3378, 4615, 6233, 8418, 11540, 15867, 21729, 29843, 41169, 56534, 77697, 106787, 147067, 203025, 280340, 387308, 535153, 739671, 1023655, 1416635, 1960813, 2716922, 3764693, 5218926, 7238715
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,3
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COMMENTS
| It is conjectured that this sequence is infinite, but this has never been proved.
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REFERENCES
| G. H. Hardy and E. M. Wright, An Introduction to the Theory of Numbers, 5th ed., Oxford Univ. Press, 1979, th. 17.
P. Ribenboim, The Little Book of Big Primes. Springer-Verlag, 1991, p. 190.
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LINKS
| C. K. Caldwell, AN AMAZING PRIME HEURISTIC A pdf file.
Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics. Landau's Problems.
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CROSSREFS
| Cf. A005574, A002496, A083844, A083845, A083846, A083848, A083849.
Sequence in context: A055002 A114097 A174246 * A034142 A008675 A027581
Adjacent sequences: A083844 A083845 A083846 * A083848 A083849 A083850
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KEYWORD
| nonn
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AUTHOR
| Harry J. Smith (hjsmithh(AT)sbcglobal.net), May 05 2003
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EXTENSIONS
| More terms from Alex Healy (ahealy(AT)post.harvard.edu), Feb 06 2005
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