A268445 - OEIS

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

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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