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 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. 0

%I

%S 3,48,813,4697,5694,6752,13773,25477,34989,125632,233328,362313,

%T 605634,673464,691659,941896,3654841,3952803,5024551,5619712,6509427,

%U 10833183,12473149

%N 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.

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

%e 3 is a term because 1^2 + 3^2 + 5^2 = 2^3 + 3^3.

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

%o (PARI) isA003325(n) = for(k=1, sqrtnint(n\2, 3), ispower(n-k^3, 3) && return(1));

%o a000447(n) = n*(4*n^2 - 1)/3;

%o for(n=1, 1e5, if(isA003325(a000447(n)), print1(n, ", ")));

%Y Cf. A000447, A003325, A269842.

%K nonn,more

%O 1,1

%A _Altug Alkan_, Mar 08 2016

%E a(10)-a(23) from _Chai Wah Wu_, Mar 16 2016

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Last modified December 13 08:08 EST 2019. Contains 329968 sequences. (Running on oeis4.)