Taylor expanding with the HP50G

[Gil]

1) Run this program previously

\<< "
Before calc limits,
Run this prog previously 
(w / no input)
" DROP RAD "Exact Mode ON:" DROP -105 CF "
Symbol result:" DROP -3 CF "CAS Object Evaluation
allows CASCOMPEVAL:" DROP -124 CF "Silent Mode OFF, if
signed res important:" DROP -120 CF "Or
'(COS(X)-1+1/2*X^2)/X
^4' 'X=0' 4 SERIES" DROP
\>>

2) {N X} PURGE
or 'N' PURGE 'X' PURGE

3) Execute what you tried before.

You should get
'-(X*N/(1-EXP(N*LN(1+X))))'