A196376 - OEIS

A196376

Positive integers a for which there is a (-4)-Pythagorean triple (a,b,c) satisfying a<=b.

1, 2, 3, 3, 4, 4, 4, 5, 5, 5, 6, 6, 7, 7, 7, 8, 8, 8, 8, 8, 9, 9, 9, 10, 10, 10, 11, 11, 11, 12, 12, 12, 12, 12, 12, 13, 13, 13, 14, 14, 14, 15, 15, 15, 15, 15, 15, 16, 16, 16, 16, 16, 16, 16, 17, 17, 17, 18, 18, 18, 19, 19, 19, 20, 20, 20, 20, 20, 20, 20, 20, 20, 21, 21

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OFFSET

1,2

COMMENTS

See A195770 for definitions of k-Pythagorean triple, primitive k-Pythagorean triple, and lists of related sequences.

LINKS

Table of n, a(n) for n=1..74.

MATHEMATICA

z8 = 900; z9 = 250; z7 = 200;

pIntegerQ := IntegerQ[#1] && #1 > 0 &;

k = -4; c[a_, b_] := Sqrt[a^2 + b^2 + k*a*b];

d[a_, b_] := If[pIntegerQ[c[a, b]], {a, b, c[a, b]}, 0]

t[a_] := Table[d[a, b], {b, a, z8}]

u[n_] := Delete[t[n], Position[t[n], 0]]

Table[u[n], {n, 1, 15}]

t = Table[u[n], {n, 1, z8}];

Flatten[Position[t, {}]]

u = Flatten[Delete[t, Position[t, {}]]];

x[n_] := u[[3 n - 2]];

Table[x[n], {n, 1, z7}] (* A196376 *)

y[n_] := u[[3 n - 1]];

Table[y[n], {n, 1, z7}] (* A196377 *)

z[n_] := u[[3 n]];

Table[z[n], {n, 1, z7}] (* A196378 *)

x1[n_] := If[GCD[x[n], y[n], z[n]] == 1, x[n], 0]

y1[n_] := If[GCD[x[n], y[n], z[n]] == 1, y[n], 0]

z1[n_] := If[GCD[x[n], y[n], z[n]] == 1, z[n], 0]

f = Table[x1[n], {n, 1, z9}];

x2 = Delete[f, Position[f, 0]] (* A196379 *)

g = Table[y1[n], {n, 1, z9}];

y2 = Delete[g, Position[g, 0]] (* A196380 *)

h = Table[z1[n], {n, 1, z9}];

z2 = Delete[h, Position[h, 0]] (* A196381 *)

CROSSREFS

Cf. A195770, A196377, A196378, A196379.

Sequence in context: A309407 A046693 A368910 * A156077 A189641 A189672

Adjacent sequences: A196373 A196374 A196375 * A196377 A196378 A196379

KEYWORD

nonn

AUTHOR

Clark Kimberling, Oct 01 2011

STATUS

approved