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A242039 List of integers b such that (a1,b,c1) and (a2,b,c2) are primitive Eisenstein triples, max(a1,b,c1,a2,c2)=b, and a1,c1,a3,c3 are distinct. 0
280, 1144, 1155, 1680, 1768, 1976, 2145, 2584, 2805, 3003, 3128, 3315, 3360, 3400, 3496, 3705, 3800, 4095, 4600, 4845, 5005, 5280, 5336, 5355, 5704, 5720, 5800, 5865, 5985, 6160, 6200, 6240, 6545, 6555, 6783, 6864, 7192, 7280, 7315, 7400, 7735, 8120, 8265, 8584, 8645, 8680, 8835, 8855, 9176, 9177, 9240, 9360, 9512, 9976 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

For Eisenstein triple see A121992.

LINKS

Table of n, a(n) for n=1..54.

EXAMPLE

280 is in the list because (93,280,247) and (19,280,271) are primitive Eisenstein triples and 280 is the largest side and no other side is equal.

Consider (3,8,7) and (5,8,7), 8 is not in the list because 7 appear in both triple.

MATHEMATICA

max = 2000;

data = Do[Sqrt[-3 a^2 + 4 c^2] // If[IntegerQ[#] && GCD[a, c] == 1, {a, (a + #)/2, c} // Sow] &, {a, max}, {c, Sqrt[3]/2 a // Ceiling, a - 1}] // Reap // Last // Last;

Select[data[[;; , 1]] // Tally, #[[2]] > 1 &][[;; , 1]]

CROSSREFS

Cf. A089025, A121992.

Sequence in context: A245208 A256708 A207075 * A234911 A234905 A187178

Adjacent sequences:  A242036 A242037 A242038 * A242040 A242041 A242042

KEYWORD

nonn

AUTHOR

Albert Lau, Aug 12 2014

STATUS

approved

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Last modified October 22 05:29 EDT 2019. Contains 328315 sequences. (Running on oeis4.)