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 A280679 The radii (a, b, c) of three primitive mutually tangent circles all touching the same straight line, with a > b > c. 2
 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 (list; graph; refs; listen; history; text; internal format)
 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 * A097488 A061046 A109256 Adjacent sequences:  A280676 A280677 A280678 * A280680 A280681 A280682 KEYWORD nonn,tabf AUTHOR Colin Barker, Jan 07 2017 STATUS approved

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Last modified April 3 23:48 EDT 2020. Contains 333207 sequences. (Running on oeis4.)