When in statistics mode, the HP 10s+ stores the sums into the its registers:
A = $x^2
B = $x
C = n
D = $y^2
E = $y
F = $xy
X = $x^2y
Y = $x^4
Where $ stands for Sigma.
The values can be recalled the same way as pressing [SHIFT] [ 1 ]. I wonder if it works the same way with the Casio fx-300ms (don't have the 300ms on me).
Edited: 10 Apr 2013, 6:43 p.m.