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 A086909 Middle side of the first primitive d-arithmetic triangle, where d=A072330(n). 10
 4, 26, 28, 52, 76, 98, 124, 134, 158, 148, 172, 206, 218, 266, 244, 316, 292, 362, 388, 388, 364, 364, 386, 398, 518, 556, 494, 532, 556, 508, 532, 602, 602, 628, 724, 676, 758, 746, 734, 854, 916, 806, 868, 916, 844, 892, 866, 868, 1036, 1022, 988, 964, 974 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 REFERENCES J. A. MacDougall, "Heron Triangles With Sides In Arithmetic Progression", Journal of Recreational Mathematics 31(3) 2002-2003, pp. 192-194. LINKS Jean-François Alcover, Table of n, a(n) for n = 1..1000 J. A. MacDougall, Heron Triangles With Sides In Arithmetic Progression, ResearchGate, 2005. MATHEMATICA terms = 1000; nmax = 12 terms; okQ[n_] := AllTrue[FactorInteger[n][[All, 1]], MatchQ[Mod[#, 12], 1|11]&]; A072330 = Select[Range[nmax], okQ]; a[n_] := Module[{a, b, c, d, p}, d = If[n <= Length[A072330], A072330[[n]], Print["nmax = ", nmax, " insufficient"]; Exit[]]; If[n==1, 4, For[b = 2d, True, b++, a = b-d; c = b+d; p = (a+b+c)/2; If[IntegerQ[p] && IntegerQ[ Sqrt[p(p-a)(p-b)(p-c)]] && GCD[a, b, c] == 1, Return[b]]]]]; a /@ Range[terms] (* Jean-François Alcover, Mar 06 2020 *) CROSSREFS Cf. A072330, A072360, A089019, A089020, A096672, A096673, A096674. Sequence in context: A276266 A276268 A306687 * A046963 A022386 A059178 Adjacent sequences:  A086906 A086907 A086908 * A086910 A086911 A086912 KEYWORD nonn AUTHOR Lekraj Beedassy, Sep 19 2003 EXTENSIONS Extended by Ray Chandler, Jul 03 2004 STATUS approved

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Last modified April 3 04:21 EDT 2020. Contains 333195 sequences. (Running on oeis4.)