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

Author

Altug Alkan, Feb 04 2016

Keywords

• nonn
• easy

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.

Examples

			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.
		

Crossrefs

Cf. A000404, A005897.

Programs

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, ", ")));