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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 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.)