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 A009129 Perimeter of more than one Pythagorean triangle. 3
 60, 84, 90, 120, 132, 144, 168, 180, 210, 240, 252, 264, 270, 280, 288, 300, 312, 330, 336, 360, 390, 396, 408, 420, 432, 440, 450, 456, 462, 468, 480, 504, 510, 520, 528, 540, 546, 552, 560, 570, 576, 588, 600, 612, 616, 624, 630, 660, 672, 680, 684, 690, 700, 720 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Charles R Greathouse IV, Table of n, a(n) for n = 1..10000 PROG (PARI) is(k)=my(m2, mm2, s); for(m=2, sqrtint(k\2), m2=2*m; mm2=2*m^2; forstep(n=if(m%2, 2, 1), min(k\m2-m, m-1), m%2+1, if(k%(mm2+m2*n)==0 && gcd(m, n)==1 && s++>1, return(1)))); 0 \\ Charles R Greathouse IV, Feb 03 2018 (PARI) list(lim)=my(v=List(), ct=Map(), m2, mm2, t); for(m=2, sqrtint(lim\2), m2=2*m; mm2=2*m^2; forstep(n=if(m%2, 2, 1), min(lim\m2-m, m-1), m%2+1, if(gcd(m, n)>1, next); t=mm2+m2*n; forstep(k=t, lim, t, mapput(ct, k, mapisdefined(ct, k))))); for(n=60, lim, if(mapisdefined(ct, n) && mapget(ct, n), listput(v, n))); ct=0; Vec(v) \\ Charles R Greathouse IV, Feb 03 2018 CROSSREFS Subsequence of A010814. Sequence in context: A123712 A178212 A182855 * A174292 A085987 A086974 Adjacent sequences:  A009126 A009127 A009128 * A009130 A009131 A009132 KEYWORD nonn AUTHOR STATUS approved

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Last modified April 12 18:58 EDT 2021. Contains 342932 sequences. (Running on oeis4.)