A271717 Integers n such that both n and n^3-1 are the sum of two positive cubes (see A003325).

9, 11664, 36864, 38134, 345744, 1750329, 4782969, 20820969, 47775744, 65804544, 95004009, 150994944, 448084224, 733055625, 1093955625, 1416167424

Offset

1,1

Comments

Values of a^3 + b^3 such that (a^3 + b^3)^3 - 1 is of the form x^3 + y^3 where a, b, x, y > 0.

38134 = 2*23*829 is the first term that is nonsquare. What are the next square terms of this sequence?

n is a member of A007412 and n^3 is a member of A003072, obviously.

Links

Table of n, a(n) for n=1..16.

Example

9 is a term because 9 = 1^3 + 2^3 and 9^3 - 1 = 6^3 + 8^3.

Prog

(PARI) isA003325(n) = for(k=1, sqrtnint(n\2, 3), ispower(n-k^3, 3) && return(1));
for(n=1, 1e7, if(isA003325(n) && isA003325(n^3-1), print1(n, ", ")));

Crossrefs

Cf. A003325, A050787, A068601.

Sequence in context: A175987 A321618 A055320 * A069501 A360762 A206461

Adjacent sequences: A271714 A271715 A271716 * A271718 A271719 A271720

Keyword

nonn,more

Author

Altug Alkan, Apr 12 2016

Extensions

a(8)-a(16) from Chai Wah Wu, Apr 17 2016

Status

approved