A268445 Integers n such that A005897(n) is the sum of two nonzero squares.

1, 2, 4, 6, 7, 8, 9, 12, 15, 16, 20, 22, 23, 26, 28, 30, 34, 36, 40, 41, 44, 47, 49, 50, 54, 55, 56, 57, 58, 63, 64, 65, 68, 70, 78, 82, 84, 86, 89, 94, 97, 98, 102, 103, 104, 105, 106, 111, 112, 113, 118, 120, 126, 127, 132, 135, 142, 143, 145, 146, 148, 151, 152, 153, 154, 156

Offset

1,2

Comments

Integers n such that number of points on surface of a 3-dimensional cube in which each face has a square grid of dots drawn on it (with n+1 points along each edge, including the corners) is the sum of two nonzero squares.

Links

Table of n, a(n) for n=1..66.

Example

1 is a term because A005897(1) = 8 = 2^2 + 2^2.
2 is a term because A005897(2) = 26 = 1^2 + 5^2.
4 is a term because A005897(4) = 98 = 7^2 + 7^2.
6 is a term because A005897(6) = 218 = 7^2 + 13^2.

Prog

(PARI) is_a000404(n) = {for( i=1, #n=factor(n)~%4, n[1, i]==3 && n[2, i]%2 && return); n && ( vecmin(n[1, ])==1 || (n[1, 1]==2 && n[2, 1]%2))}
a005897(n) = if(n, 6*n^2+2, 1);
for(n=0, 200, if(is_a000404(a005897(n)), print1(n, ", ")));

Crossrefs

Cf. A000404, A005897.

Sequence in context: A285416 A284958 A014530 * A053663 A324561 A288258

Adjacent sequences: A268442 A268443 A268444 * A268446 A268447 A268448

Keyword

nonn,easy

Author

Altug Alkan, Feb 04 2016

Status

approved