# Forcing nice positions of summation Σ 's under and overscript in FractionBox

Apologies if this has been asked before.

The expression

expr = Defer @ Sum[
FractionBox[
z^p
, p!
] FractionBox[
Sum[k^(p + s), {k, 1, n}]
, Binomial[p + s, p]
]
, {p, 0, Infinity}
]


produces

expr //DisplayForm //TraditionalForm


using DisplayFrom and TraditionalForm (in combination with Defer and HoldForm). Is there a way to force Mathematica to display the second sum in the numerator nicely, similarly to the first sum (i.e. underscript under and on top of the summation).

Thank you for all help.

I think you're looking for the LimitsPositioning suboption to UnderoverscriptBoxOptions. For example:

expr = Defer @ Sum[
Defer[z^p/p!] Defer[Sum[k^(p+s),{k,1,n}]/Binomial[p+s,p]],
{p, 0, Infinity}
];


Using the LimitsPositioning option:
Style[expr, UnderoverscriptBoxOptions -> {LimitsPositioning -> False}] //TraditionalForm