Summation on HP 42S

[pier4r]

for sum(x^2 - 3*x)

one could actually do:
sum(x^2 ) (closed formula) minus
3*sum(x) (closed formula).

namely here: https://brilliant.org/wiki/sum-of-n-n2-or-n3/

PS: brilliant has so much potential that they don't use. So many interesting problems buried by a poor layout sometimes.