This bug originates from Maxima: if you evaluate

```
sum(binomial(1,n),n,0,oo)
```

then it returns

```
from sage.calculus.calculus import symbolic_sum
symbolic_sum(binomial(1,n),n,0,oo)
```

which calls

```
maxima_calculus.sr_sum(binomial(1,n),n,0,oo)
```

which returns

```
from sage.interfaces.maxima_lib import max_to_sr, maxima_eval, max_ratsimp, max_simplify_sum, max_sum, sr_to_max
args = [binomial(1,n), n, 0, oo]
max_to_sr(maxima_eval([[max_ratsimp],[[max_simplify_sum],([max_sum],[sr_to_max(SR(a)) for a in args])]]))
```

Indeed we can see the bug in Maxima's `simplify_sum`

:

```
(%i1) load("simplify_sum");
(%i2) simplify_sum(sum(binomial(1,n),n,0,inf));
(%o2) 3
```

I reported it upstream at Maxima, simplify_sum(sum(binomial(1,n),n,0,inf)) gives 3 instead of 2, and it is now tracked as trac ticket #27092.