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A268445 Integers n such that A005897(n) is the sum of two nonzero squares. 0
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 (list; graph; refs; listen; history; text; internal format)
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 A288258 A075313

Adjacent sequences:  A268442 A268443 A268444 * A268446 A268447 A268448

KEYWORD

nonn,easy

AUTHOR

Altug Alkan, Feb 04 2016

STATUS

approved

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Last modified February 21 01:09 EST 2019. Contains 320364 sequences. (Running on oeis4.)