# [seqfan] Comment in A173299

Klaus Brockhaus klaus-brockhaus at t-online.de
Sat Mar 6 11:00:30 CET 2010

```Vincenzo,

your comment in the recently added sequence A173299 needs revision.

%S A173299
1,2,5,7,19,13,71,97,265,181,989,1351,3691,2521,13775,18817,51409,35113,
%N A173299 Numerators of fractions x^n + y^n, where x + y = 1 and
x^2 + y^2 = 2.
%C A173299 x*y=(-1/2); (x+y)^5=1-[(-25+10)/4]=1+15/4=19/4. [From
Vincenzo Librandi
(vincenzo.librandi(AT)tin.it), Feb 21 2010]
%O A173299 1,2

"(x+y)^5= ... =19/4" is oviously wrong since x+y = 1; (x+y)^5 has to be
replaced with x^5+y^5. After that, one can *guess* that the line is
intended as an illustation of how to compute a(5). However, some
explanatory *words* are required. Perhaps something like

Using the equations given in the definition, and x*y = -1/2 which
follows from them, x^5+y^5 can be transformed step by step to
.....(perhaps some intermediate results)..... 1-((-25+10)/4) = 1+15/4 =
19/4. Therefore a(5) = 19.

would do (no square brackets please!). Now it would be clear that this
is an *example*. And for examples there are %e lines!

Please make some changes to that effect!

Klaus

```