A224773 - OEIS

%I #11 Mar 07 2023 10:20:47

%S 7,13,15,19,21,23,25,27,31,33,35,37,39,43,45,47,49,53,55,57,59,61,63,

%T 67,69,71,73,75,77,79,81,83,85,87,89,91,93,95,97,99,101,103,105,107,

%U 109,111,113,115,117,119,121,123,125,127,129,131,133,135,137,139

%N One half of the even terms of A224771.

%C 2*a(n), n >= 1, gives all even numbers representable as a primitive sum of three distinct nonzero squares.

%C The numbers a(n) are of interest in a problem related to integer solutions for the curvatures of the Descartes-Steiner circle theorem.

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/DescartesCircleTheorem.html">Descartes Circle Theorem</a>.

%F a(n) is one half of the n-th even term of A224771.

%e a(1) = 7 because the first even term of A224771 is 14 (m = 1).

%e a(9) = 31 because 62 is the ninth even term of A224771 (m = 18).

%Y Cf. A224771.

%K nonn

%O 1,1

%A _Wolfdieter Lang_, Apr 19 2013