

A198463


Consider triples a<=b<c where (a^2+b^2c^2)/(cab) =3, ordered by a and then b; sequence gives b values.


0



3, 7, 12, 18, 6, 11, 25, 15, 33, 42, 10, 15, 52, 30, 63, 36, 75, 14, 19, 27, 88, 102, 75, 117, 18, 23, 42, 65, 133, 150, 30, 39, 168, 22, 27, 60, 92, 187, 102, 207, 42, 54, 228, 22, 26, 31, 81, 250, 51, 135, 273, 147, 297, 30, 35, 105, 322, 45, 66, 84, 348
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OFFSET

1,1


COMMENTS

The definition can be generalized to define Pythagorean ktriples a<=b<c where (a^2+b^2c^2)/(cab)=k, or where for some integer k, a(a+k) + b(b+k) = c(c+k).
If a, b and c form a Pythagorean ktriple, then na, nb and nc form a Pythagorean nktriple.
A triangle is defined to be a Pythagorean ktriangle if its sides form a Pythagorean ktriple.
If a, b and c are the sides of a Pythagorean ktriangle ABC with a<=b<c, then cos(C) = k/(a+b+c+k) which proves that such triangles must be obtuse when k>0 and acute when k<0. When k=0, the triangles are Pythagorean, as in the Beiler reference and Ron Knottās link. For all k, the area of a Pythagorean ktriangle ABC with a<=b<c equals sqrt((2ab)^2(k(a+bc))^2))/4.


REFERENCES

A. H. Beiler, Recreations in the Theory of Numbers, Dover, New York, 1964, pp. 104134.


LINKS

Table of n, a(n) for n=1..61.
Ron Knott, Pythagorean Triples and Online Calculators


EXAMPLE

2*5 + 3*6 = 4*7
3*6 + 7*10 = 8*11
4*7 +12*15 = 13*16
5*8 + 18*21 = 19*22
6*9 = 6*9 = 9*12
6*9 = 11*14 = 13*16


PROG

(True BASIC)
input k
for a = (abs(k)k+4)/2 to 40
for b = a to (a^2+abs(k)*a+2)/2
let t = a*(a+k)+b*(b+k)
let c =int((k+ (k^2+4*t)^.5)/2)
if c*(c+k)=t then print a; b; c,
next b
print
next a
end


CROSSREFS

Cf. A103606, A198454A198469.
Sequence in context: A298022 A227133 A170883 * A140778 A095115 A141214
Adjacent sequences: A198460 A198461 A198462 * A198464 A198465 A198466


KEYWORD

nonn


AUTHOR

Charlie Marion, Nov 26 2011


STATUS

approved



