HP49-HP50 : 'n^a' 'n' 1 5 1 SEQ with no LN?

[Gil]

Suppose the following program
« { } 2 5
FOR i i a ^ +
NEXT
»

Its execution gives
{ '2^a' '3^a' '4^a' '5^a' } <1>

Now
'n^a' n 2 4 1 SEQ

gives { 'EXP(a*LN(2))' 'EXP(a*LN(3))' 'EXP(2*a*LN(2))'} <2>

Using SEQ
how can I get the form given in <1>
(with no LN)?