%I A077020
%S A077020 1,1,1,3,1,5,7,3,17,11,23,45,1,91,89,93,271,85,457,627,287,1541,967,
%T A077020 2115,4049,181,8279,7917,8641,24475,7193,41757,56143,27371,139657,
%U A077020 84915,194399,364229,24569,753027,703889,802165,2209943,605613
%N A077020 a(n) is the unique odd positive solution x of 2^n = 7x^2+y^2.
%D A077020 A. Engel, Problem-Solving Strategies. p. 126.
%H A077020 Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/
               DiophantineEquation2ndPowers.html">Diophantine Equations 2nd Powers</
               a>
%e A077020 a(3)=1 since 2^3=8=7*1^2+1^2, a(6)=3 since 2^6=64=7*3^2+1^2.
%Y A077020 a(n)=abs(A001607(n-2)).
%Y A077020 Cf. A077021.
%Y A077020 Sequence in context: A134249 A001607 A167433 this_sequence A107920 A159285 
               A021080
%Y A077020 Adjacent sequences: A077017 A077018 A077019 this_sequence A077021 A077022 
               A077023
%K A077020 nonn
%O A077020 3,4
%A A077020 Ed Pegg Jr. (ed(AT)mathpuzzle.com), Oct 17, 2002