Thank you both for the answers,

I found another problematic example

sage:E1=EllipticCurve([0,0,0,37,18]);E1;S=E1.integral_points();S;
Elliptic Curve defined by y^2 = x^3 + 37*x + 18 
over Rational Field 
[(2 : 10 : 1), (126 : 1416 : 1)]



and 

R = E1(64039202,512470496030);M=E1(2,10 );3*M==R
True

Both examples are from the paper 
of Don Zagier: Large integral points on Elliptic curves 
<http://people.mpim-bonn.mpg.de/zagier/files/doi/10.2307/2007900/fulltext.pdf>

Also, I tried the previous examples in the online calculator of magma and 
seems that magma works fine.
  magma: E := EllipticCurve([0,0,0,37,18]);
 IntegralPoints(E);
[ (2 : 10 : 1), (126 : 1416 : 1), (64039202 : 512470496030 : 1) ]
[ <(2 : 10 : 1), 1>, <(126 : 1416 : 1), 1>, 
<(64039202 : 512470496030 : 1), 1> ]



I use this function a lot and  
I think many people (heavily) use this function
for their research. I was not aware of the problems of this function :(

I am wondering if this bug affects other functions concerning 
elliptic curves?

Thanks again for the answers
Costas. 





On Wednesday, December 14, 2016 at 10:25:25 PM UTC+2, Nils Bruin wrote:
>
> On Wednesday, December 14, 2016 at 12:09:36 PM UTC-8, John Cremona wrote:
>>
>>
>> Thanks for the bug report.  As Nils pointed out there are known bugs 
>> in the integral point code which cause solutions to be missed.
>
>
> Just to make clear: I wasn't taking a jibe at sage/or John on this, and I 
> wasn't previously aware there are bugs in the integral points code in Sage. 
> I was just observing that in the past 20 years, any computer algebra 
> package that implements integral point finding on elliptic curves has had 
> significant errors (of the type reported here). Apparently it's something 
> that is particularly hard to get reliably correct.
>

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