A280679 The radii (a, b, c) of three primitive mutually tangent circles all touching the same straight line, with a > b > c.

36, 9, 4, 144, 16, 9, 225, 100, 36, 400, 25, 16, 784, 441, 144, 900, 36, 25, 1225, 196, 100, 1600, 576, 225, 1764, 49, 36, 2025, 1296, 400, 3136, 64, 49, 3969, 324, 196, 4356, 3025, 900, 4900, 900, 441, 5184, 81, 64, 5929, 1936, 784, 7056, 3600, 1225

Offset

1,1

Links

Colin Barker, Table of n, a(n) for n = 1..3000

Eric Weisstein's World of Mathematics, Tangent Circles

Formula

The first few triples are [36, 9, 4], [144, 16, 9], [225, 100, 36], [400, 25, 16].

Prog

(PARI)
a280679(amax) = {
  my(L=List());
  for(a=1, amax,
    for(b=1, a-1,
      c=(1/(1/a + 1/b))^2;
      if(type(c)=="t_INT" && gcd([a^2, b^2, c])==1,
        listput(L, [a^2, b^2, c])
      )
    )
  );
  Vec(L)
}
concat(a280679(100))

Crossrefs

Cf. A265189, A280680.

Sequence in context: A255868 A289138 A181759 * A343921 A097488 A061046

Adjacent sequences: A280676 A280677 A280678 * A280680 A280681 A280682

Keyword

nonn,tabf

Author

Colin Barker, Jan 07 2017

Status

approved