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A255018 Smallest number that is the sum of 3 nonnegative cubes in exactly n ways. 1
4, 0, 216, 5104, 13896, 161568, 1259712, 2016496, 2562624, 14926248, 58995000, 34012224, 150547032, 471960000, 119095488, 1259712000, 952763904, 5159780352, 3974344704, 2176782336 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

LINKS

Table of n, a(n) for n=0..19.

EXAMPLE

a(0) = 4 because the smallest number that cannot be represented as a sum of 3 nonnegative cubes is 4.

a(1) = 0 is the sum of three 0's.

a(2) = 216 = 3^3 + 4^3 + 5^3 = 6^3 + 0 + 0.

a(3) = 5104 = 1 + 12^3 + 15^3 = 2^3 + 10^3 + 16^3 = 9^3 + 10^3 + 15^3.

PROG

(Python)

TOP = 60000000

a = [0]*TOP

for b in range(TOP):

  b3 = b**3

  if b3*3>=TOP: break

for c in range(b, TOP):

    c3 = b3 + c**3

    if c3>=TOP: break

for d in range(c, TOP):

      res = c3 + d**3

      if res>=TOP: break

      #if res==5104: print b, c, d

      a[res] += 1

m = max(a)

print m

r = [-1] * (m+1)

for i in range(TOP):

    if r[a[i]]==-1:  r[a[i]]=i

print r

CROSSREFS

Cf. A000578, A000446, A011541, A025418, A025419.

Sequence in context: A138734 A265596 A119010 * A176050 A099841 A013452

Adjacent sequences:  A255015 A255016 A255017 * A255019 A255020 A255021

KEYWORD

nonn,more

AUTHOR

Alex Ratushnyak, Feb 25 2015

STATUS

approved

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Last modified May 31 13:01 EDT 2020. Contains 334748 sequences. (Running on oeis4.)