login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A273488 Number of triples (x,y,z) with x,y,z in the set {0,...,n-1} such that x + y + z is a cube and x^3 + 5*y^3 + 24*z^3 == 2 (mod n). 2
1, 2, 1, 1, 2, 5, 5, 3, 6, 6, 7, 2, 13, 8, 12, 10, 17, 2, 15, 9, 18, 24, 12, 8, 12, 23, 15, 11, 21, 25, 30, 14, 29, 27, 23, 25, 34, 29, 42, 19, 42, 35, 57, 16, 69, 45, 41, 23, 45, 43, 43, 34, 60, 77, 52, 23, 53, 64, 74, 33 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Conjecture: For any positive integer n, the set {x^3 + 5*y^3 + 24*z^3: x,y,z = 0,...,n-1 and x + y + z is a cube} contains a complete system of residues modulo n.

See also A273287 for a similar conjecture.

LINKS

Zhi-Wei Sun, Table of n, a(n) for n = 1..350

EXAMPLE

a(2) = 2 since 0^3 + 5*0^3 + 24*0^3 == 2 (mod 2) with 0 + 0 + 0 = 0^3, and 0^3 + 5*0^3 + 24*1^3 == 2 (mod 2) with 0 + 0 + 1 = 1^3.

a(3) = 1 since 0^3 + 5*1^3 + 24*0^3 == 2 (mod 3) with 0 + 1 + 0 = 1^3.

a(4) = 1 since 3^3 + 5*3^3 + 24*2^3 == 2 (mod 4) with 3 + 3 + 2 = 2^3.

MATHEMATICA

CQ[n_]:=CQ[n]=IntegerQ[n^(1/3)]

In[2]:= Do[r=0; Do[If[Mod[x^3+5y^3+24z^3-2, n]==0&&CQ[x+y+z], r=r+1], {x, 0, n-1}, {y, 0, n-1}, {z, 0, n-1}]; Print[n, " ", r]; Continue, {n, 1, 60}]

CROSSREFS

Cf. A000578, A273287.

Sequence in context: A289772 A283615 A216396 * A117848 A025242 A163982

Adjacent sequences:  A273485 A273486 A273487 * A273489 A273490 A273491

KEYWORD

nonn

AUTHOR

Zhi-Wei Sun, Aug 28 2016

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified July 13 17:54 EDT 2020. Contains 335689 sequences. (Running on oeis4.)