A280680 The square roots of the radii (a, b, c) of three primitive mutually tangent circles all touching the same straight line, with a > b > c.
6, 3, 2, 12, 4, 3, 15, 10, 6, 20, 5, 4, 28, 21, 12, 30, 6, 5, 35, 14, 10, 40, 24, 15, 42, 7, 6, 45, 36, 20, 56, 8, 7, 63, 18, 14, 66, 55, 30, 70, 30, 21, 72, 9, 8, 77, 44, 28, 84, 60, 35, 88, 33, 24, 90, 10, 9, 91, 78, 42, 99, 22, 18, 104, 65, 40
Offset: 1
Examples
The first few triples are [6, 3, 2], [12, 4, 3], [15, 10, 6], [20, 5, 4].
Links
- Colin Barker, Table of n, a(n) for n = 1..3000
- Eric Weisstein's World of Mathematics, Tangent Circles
Programs
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PARI
a280680(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,b,sqrtint(c)]) ) ) ); Vec(L) } concat(a280680(100))