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A130110 Rearrangement of natural numbers such that each four terms sum up to a perfect square. 3
1, 2, 3, 10, 4, 5, 6, 21, 7, 8, 9, 12, 11, 13, 14, 26, 15, 16, 17, 33, 18, 19, 20, 24, 22, 23, 25, 30, 27, 28, 29, 37, 31, 32, 34, 47, 35, 36, 38, 60, 39, 40, 41, 49, 42, 43, 44, 67, 45, 46, 48, 57, 50, 51, 52, 72, 53, 54, 55, 63, 56, 58, 59, 83, 61, 62, 64, 69, 65, 66, 68, 90 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

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

EXAMPLE

1+2+3+10=16, 4+5+6+21=36, 7+8+9+12=36, 11+13+14+26=64.

MATHEMATICA

s={}; ra=Range[2000]; Do[su=ra[[1]]+ra[[2]]+ra[[3]]; c=4; While[ !IntegerQ[Sqrt[su+ra[[c]]]], c++ ]; rac=ra[[c]]; s=Join[s, {ra[[1]], ra[[2]], ra[[3]], rac}]; ra=Complement[ra, {ra[[1]], ra[[2]], ra[[3]], rac}], {50}]; s

CROSSREFS

Cf. A130108, A130109, A130111.

Sequence in context: A319157 A153702 A280941 * A031275 A306465 A276104

Adjacent sequences:  A130107 A130108 A130109 * A130111 A130112 A130113

KEYWORD

nonn

AUTHOR

Zak Seidov, May 08 2007

STATUS

approved

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Last modified March 26 01:08 EDT 2019. Contains 321479 sequences. (Running on oeis4.)