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Numbers X such that X^2 + Y^2 = 3^(2*k) + 1 and X > Y > 0 and k is the ternary digit length of X-1.
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%I #20 Feb 17 2024 11:28:08

%S 3,9,21,27,71,81,195,233,243,711,729,1583,1749,2157,2187,6561,14829,

%T 15747,19629,19683,57609,59049,141717,154727,175537,177147,385559,

%U 394471,414649,422729,446489,462601,468919,482759,488431,504161,515649,524559,529599,530529

%N Numbers X such that X^2 + Y^2 = 3^(2*k) + 1 and X > Y > 0 and k is the ternary digit length of X-1.

%C The number of terms for a given k is A025435(3^(2*k)+1).

%H A.H.M. Smeets, <a href="/A369768/b369768.txt">Table of n, a(n) for n = 1..191</a>

%Y Cf. A004018, A025435.

%Y Cf. A369703 (base 2), this sequence (base 3), A369769 (base 5), A368418 (base 10).

%K nonn,base

%O 1,1

%A _A.H.M. Smeets_, Jan 31 2024