A130109 Rearrangement of natural numbers such that each two terms sum up to a perfect square.

1, 3, 2, 7, 4, 5, 6, 10, 8, 17, 9, 16, 11, 14, 12, 13, 15, 21, 18, 31, 19, 30, 20, 29, 22, 27, 23, 26, 24, 25, 28, 36, 32, 49, 33, 48, 34, 47, 35, 46, 37, 44, 38, 43, 39, 42, 40, 41, 45, 55, 50, 71, 51, 70, 52, 69, 53, 68, 54, 67, 56, 65, 57, 64, 58, 63, 59, 62, 60, 61, 66, 78

Offset

1,2

Links

Table of n, a(n) for n=1..72.

Example

1+3=4, 2+7=9, 4+5=9, 6+10=16, 8+17=25.

Mathematica

s={}; ra=Range[2000]; Do[su=ra[[1]]; c=2; While[ !IntegerQ[Sqrt[su+ra[[c]]]], c++ ]; rac=ra[[c]]; s=Join[s, {ra[[1]], rac}]; ra=Complement[ra, {ra[[1]], rac}], {133}]; s

Crossrefs

Cf. A130108, A130110, A130111.

Sequence in context: A129187 A166532 A135542 * A334998 A153151 A175057

Adjacent sequences: A130106 A130107 A130108 * A130110 A130111 A130112

Keyword

nonn

Author

Zak Seidov, May 08 2007

Status

approved