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A274132 Numbers n such that n^k is the sum of three positive cubes for all positive integers k. 0
134, 153, 216, 225, 244, 251, 288, 342, 368, 405, 408, 415, 528, 532, 540, 577, 645, 729, 750, 755, 764, 855, 863, 882, 918, 919, 946, 972, 980, 1065, 1072, 1080, 1126, 1224, 1250, 1333, 1351, 1422, 1457, 1464, 1466, 1520, 1539, 1548, 1581, 1611, 1701, 1728 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Cubes in this sequence are 216, 729, 1728, 5832, 6859, ...

If n, n^2 and n^3 are sums of three positive cubes, then n is in the sequence, because if n^k = a^3 + b^3 + c^3, n^(3+k) = (na)^3 + (nb)^3 + (nc)^3. - Robert Israel, Jul 02 2019

LINKS

Table of n, a(n) for n=1..48.

EXAMPLE

134 is a term because 134 = 1^3 + 2^3 + 5^3, 134^2 = 10^3 + 11^3 + 25^3, 134^3 = 44^3 + 102^3 + 108^3, 134^4 = 134^3 + (2*134)^3 + (5*134)^3, 134^5 = 1340^3 + (11*134)^3 + (25*134)^3, ...

MAPLE

A3072:= proc(n) local a, b, c;

  for a from 1 while 3*a^3<=n do

   for b from a while a^3 + 2*b^3 <= n do

     c:= floor((n-a^3-b^3)^(1/3));

     if a^3+b^3+c^3=n then return true fi;

od od;

false

end proc:

filter:= n -> A3072(n) and A3072(n^2) and A3072(n^3):

select(filter, [$1..2000]); # Robert Israel, Jul 02 2019

CROSSREFS

Cf. A003072.

Sequence in context: A191715 A208626 A061491 * A252133 A255795 A048128

Adjacent sequences:  A274129 A274130 A274131 * A274133 A274134 A274135

KEYWORD

nonn

AUTHOR

Altug Alkan, Jun 10 2016

STATUS

approved

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Last modified February 27 13:18 EST 2020. Contains 332306 sequences. (Running on oeis4.)