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A103246
Numbers y, without duplication, in Pythagorean triples x,y,z where x,y,z are relatively prime composite numbers.
7
21, 27, 33, 55, 57, 63, 75, 77, 81, 87, 91, 93, 99, 105, 111, 115, 117, 119, 123, 125, 129, 133, 135, 143, 147, 153, 155, 161, 165, 171, 177, 183, 185, 187, 189, 195, 201, 203, 207, 213, 215, 217, 219, 225, 235, 237, 243, 247, 249, 253, 255, 259, 265, 267, 273
OFFSET
1,1
COMMENTS
The example is the smallest such triple in terms of x. In terms of y, 220^2 + 21^2 = 221^2 is the smallest such triple.
Evidently the triples here are ordered so that x is even and y is odd. - Robert Israel, Oct 22 2018
LINKS
MathForFun, Pythagorean triples [Cached copy]
Chenglong Zou, Peter Otzen, Cino Hilliard, Pythagorean triplets, digest of 6 messages in mathfun Yahoo group, Mar 19, 2005.
EXAMPLE
x=16, y=63, 16^2 + 63^2 = 65^2. 63 is the 6th entry in the list.
MAPLE
N:= 1000: # to get all terms <= N
Res:= NULL:
for m from 1 to N by 2 do
for n from 1 to m-2 by 2 while m*n <= N do
if igcd(m, n) > 1 then next fi;
if not isprime(m*n) and not isprime((m^2+n^2)/2) then
Res:= Res, m*n;
fi
od od:
sort(convert({Res}, list)); # Robert Israel, Oct 22 2018
PROG
(PARI) pythtri(n) = { local(a, b, c=0, k, x, y, z, vy, j); w = vector(n*n); for(a=1, n, for(b=1, n, x=2*a*b; y=b^2-a^2; z=b^2+a^2; if(y > 0 &!isprime(x) &!isprime(y) &!isprime(z), if(gcd(x, y)==1&gcd(x, z)==1&gcd(y, z)==1, c++; w[c]=y; ) ) ) ); vy=vector(c); w=vecsort(w); for(j=1, n*n, if(w[j]>0, k++; vy[k]=w[j]; ) ); for(j=1, 200, if(vy[j+1]<>vy[j], print1(vy[j]", ")) ) }
CROSSREFS
Sequence in context: A364414 A365081 A352096 * A206347 A362008 A247316
KEYWORD
easy,nonn
AUTHOR
Cino Hilliard, Mar 19 2005
STATUS
approved