A337366 Number of representations of A036691(n) as a sum of 3 nonnegative cubes.

1, 0, 1, 1, 2, 1, 1, 2, 1, 4, 6, 3, 8, 8, 14, 7

Offset

0,5

Comments

Conjecture I: a(n) = 0 only for n = 1. That is, any product of first n > 1 composite numbers is a sum of at most 3 positive cubes. For example,

A036691(100) = 2563573191821442299652988946477367093137353211904000000000^3 + 21431289850849406740917647451954098598503667204096000000000^3 + 26409890400237152457638095665189553529771293409280000000000^3.

Conjecture II: For any term t >= 1, there are only finitely many values of n such that a(n) = t.

Links

Table of n, a(n) for n=0..15.

Formula

a(n) = A025447(A036691(n)).

Example

a(4) = 2 because A036691(4) = 1728 = 12^3 = 6^3 + 8^3 + 10^3.

Mathematica

A036691 = Join[{1}, FoldList[Times, Select[Range[20], CompositeQ]]];
Table[Length@ PowersRepresentations[A036691[[n]], 3, 3], {n, 10}] (* Robert Price, Sep 08 2020 *)

Crossrefs

Cf. A025447, A036691, A226955, A267414.

Sequence in context: A050473 A057593 A117008 * A153917 A326407 A126127

Adjacent sequences: A337363 A337364 A337365 * A337367 A337368 A337369

Keyword

nonn,more

Author

Altug Alkan, Aug 25 2020

Status

approved