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a(n)^2 + 1 is largest prime of the form x^2 + 1 <= 2^n.
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%I #13 Nov 04 2013 03:28:08

%S 1,1,2,2,4,6,10,14,20,26,40,56,90,126,180,250,350,496,716,1010,1440,

%T 2034,2896,4086,5774,8184,11566,16380,23166,32766,46326,65534,92666,

%U 131070,185354,262130,370714,524260,741454,1048554,1482904,2097146

%N a(n)^2 + 1 is largest prime of the form x^2 + 1 <= 2^n.

%C It is conjectured that this sequence is infinite, but this has never been proved.

%C Ratio of successive terms appears to approach sqrt(2). - _Bill McEachen_, Nov 03 2013

%D G. H. Hardy and E. M. Wright, An Introduction to the Theory of Numbers, 5th ed., Oxford Univ. Press, 1979, th. 17.

%D P. Ribenboim, The Little Book of Big Primes. Springer-Verlag, 1991, p. 190.

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/LandausProblems.html">Landau's Problems.</a>

%Y Cf. A005574, A002496, A083844, A083845, A083846, A083847, A083849.

%K nonn

%O 1,3

%A _Harry J. Smith_, May 05 2003