A181404 Total number of positive integers below 10^n requiring 8 positive cubes in their representation as sum of cubes.

0, 3, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15

Offset: 1

Author

Martin Renner, Jan 28 2011

Keywords

• nonn
• easy

Comments

Also continued fraction expansion of (9+sqrt(229))/74. - Bruno Berselli, Sep 09 2011

Links

• Eric Weisstein's World of Mathematics, Waring's Problem
• Index entries for linear recurrences with constant coefficients, signature (1).

Crossrefs

Cf. A018889, A010854.

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

Programs

Mathematica

PadRight[{0, 3}, 100, 15] (* Paolo Xausa, May 24 2024 *)

PARI

a(n)=if(n>2,15,3*n-3) \\ Charles R Greathouse IV, Oct 07 2015

Formula

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

a(n) = 15 for n > 2. - Charles R Greathouse IV, Sep 09 2011

G.f.: 3*x^2*(1+4*x)/(1-x). - Bruno Berselli, Sep 09 2011

E.g.f.: 3*(5*(exp(x) - 1 - x) - 2*x^2). - Stefano Spezia, May 21 2024

Extensions

a(5)-a(7) from Lars Blomberg, May 04 2011