A287166 - OEIS

%I #5 May 20 2017 21:49:23

%S 7,22,31,37,45,67,55,61,69,70,79,82,94,108,85,93,103,106,111,132,109,

%T 126,139,117,147,146,130,145,144,133,153,167,141,154,160,172,159,166,

%U 187,157,177,174,175,0,178,165

%N Smallest number with exactly n representations as a sum of 7 nonzero squares or 0 if no such number exists.

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

%H <a href="/index/Su#ssq">Index entries for sequences related to sums of squares</a>

%F A025431(a(n)) = n for a(n) > 0.

%e a(1) = 7 because 7 is the smallest number with exactly 1 representation as a sum of 7 nonzero squares: 7 = 1^2 + 1^2 + 1^2 + 1^2 + 1^2 + 1^2 + 1^2;

%e a(2) = 22 because 22 is the smallest number with exactly 2 representations as a sum of 7 nonzero squares: 22 = 1^2 + 1^2 + 1^2 + 1^2 + 1^2 + 1^2 + 4^2 = 1^2 + 1^2 + 2^2 + 2^2 + 2^2 + 2^2 + 2^2, etc.

%Y Cf. A016032, A025414, A025416, A025431, A080654, A287165, A287167.

%K nonn

%O 1,1

%A _Ilya Gutkovskiy_, May 20 2017