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A130109 Rearrangement of natural numbers such that each two terms sum up to a perfect square. 3
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 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
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
Sequence in context: A129187 A166532 A135542 * A334998 A153151 A175057
KEYWORD
nonn
AUTHOR
Zak Seidov, May 08 2007
STATUS
approved

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Last modified March 19 07:17 EDT 2024. Contains 370954 sequences. (Running on oeis4.)