A089020 First value y satisfying x^2 - 3*y^2 = d^2, where d=A072330(n).

1, 4, 3, 7, 5, 8, 11, 16, 20, 7, 13, 20, 12, 44, 9, 51, 17, 52, 57, 55, 19, 11, 16, 28, 72, 91, 36, 65, 69, 13, 23, 68, 20, 25, 105, 15, 88, 76, 44, 120, 145, 40, 87, 119, 29, 85, 24, 17, 155, 132, 93, 31, 44, 104, 52, 92, 95, 19, 140, 200, 28, 105, 231, 35, 100, 185, 105, 120

Offset

1,2

Links

Jean-François Alcover, Table of n, a(n) for n = 1..1000

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, 1, For[b = 2 d, 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[ Sqrt[b^2 - 4 d^2]/(2 Sqrt[3])]]]]];
a /@ Range[terms] (* Jean-François Alcover, Mar 07 2020 *)

Crossrefs

For corresponding x see A089019.

Cf. A072330, A072360, A086909, A089019, A096672, A096673, A096674.

Sequence in context: A365214 A257876 A093051 * A046560 A205392 A131413

Adjacent sequences: A089017 A089018 A089019 * A089021 A089022 A089023

Keyword

nonn

Author

Lekraj Beedassy, Nov 04 2003

Extensions

Extended by Ray Chandler, Jul 03 2004

Status

approved