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Total number of positive integers below 10^n requiring 8 positive cubes in their representation as sum of cubes.
10

%I #33 May 24 2024 16:28:00

%S 0,3,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,

%T 15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,

%U 15,15,15,15,15,15,15,15,15,15,15,15,15,15,15

%N Total number of positive integers below 10^n requiring 8 positive cubes in their representation as sum of cubes.

%C Also continued fraction expansion of (9+sqrt(229))/74. - _Bruno Berselli_, Sep 09 2011

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

%H <a href="/index/Rec#order_01">Index entries for linear recurrences with constant coefficients</a>, signature (1).

%F A061439(n) + A181375(n) + A181377(n) + A181379(n) + A181381(n) + A181400(n) + A181402(n) + a(n) + A130130(n) = A002283(n).

%F a(n) = 15 for n > 2. - _Charles R Greathouse IV_, Sep 09 2011

%F G.f.: 3*x^2*(1+4*x)/(1-x). - _Bruno Berselli_, Sep 09 2011

%F E.g.f.: 3*(5*(exp(x) - 1 - x) - 2*x^2). - _Stefano Spezia_, May 21 2024

%t PadRight[{0, 3}, 100, 15] (* _Paolo Xausa_, May 24 2024 *)

%o (PARI) a(n)=if(n>2,15,3*n-3) \\ _Charles R Greathouse IV_, Oct 07 2015

%Y Cf. A018889, A010854.

%Y Cf. A002283, A061439, A130130, A181375, A181377, A181379, A181381, A181400, A181402.

%K nonn,easy

%O 1,2

%A _Martin Renner_, Jan 28 2011

%E a(5)-a(7) from _Lars Blomberg_, May 04 2011