A270005 Integers n such that 1^2 + 3^2 + 5^2 + ... + (2*n-1)^2 = x^3 + y^3 has a solution in positive integers x and y.

3, 48, 813, 4697, 5694, 6752, 13773, 25477, 34989, 125632, 233328, 362313, 605634, 673464, 691659, 941896, 3654841, 3952803, 5024551, 5619712, 6509427, 10833183, 12473149

Offset

1,1

Comments

Integers n such that n*(4*n^2 - 1)/3 is the sum of 2 positive cubes.

Links

Table of n, a(n) for n=1..23.

Example

3 is a term because 1^2 + 3^2 + 5^2 = 2^3 + 3^3.
48 is a term because 1^2 + 3^2 + 5^2 + ... + 95^2 = 31^3 + 49^3.

Prog

(PARI) isA003325(n) = for(k=1, sqrtnint(n\2, 3), ispower(n-k^3, 3) && return(1));
a000447(n) = n*(4*n^2 - 1)/3;
for(n=1, 1e5, if(isA003325(a000447(n)), print1(n, ", ")));

Crossrefs

Cf. A000447, A003325, A269842.

Sequence in context: A007654 A001080 A099852 * A218382 A195635 A203427

Adjacent sequences: A270002 A270003 A270004 * A270006 A270007 A270008

Keyword

nonn,more

Author

Altug Alkan, Mar 08 2016

Extensions

a(10)-a(23) from Chai Wah Wu, Mar 16 2016

Status

approved