Returning more than 12 digits for a result

[brickviking]

I thought I'd post this as a new thread instead of appending to my previous discussion, as that got a bit off what I was trying to do.

A while ago, I came across a discussion on these forums that allowed my HP-50G to give me far more than the customary 10 digits for an arbitrary equation, though I can't remember what the equation was, nor the RPL code backing it up. In this particular case, I'm after more than 12 digits of pi. However, I can't find that discussion anywhere, though pier4r has something somewhat related. I've also not been able to duplicate that feat since except by running PI50G.

I ran across this video about manually calculating pi yesterday, and I decided to run that formula through my calculator (the Chudnovsky algorithm). I started off nice and simply and set the sum (see formula) to k=2, a small number that should have resulted in about 21 correct digits. Unfortunately, I was disappointed when my calculator coughed up a result of 3.14159265359 for k=2, which while correct as far as it goes, was nowhere near the number of digits I'd intended for a result. Is there any way to cough up more digits from that formula without using a multiple-precision library, i.e. only using what's available with the stock hp-50G? I'd tried both Exact mode and Approx mode, but I'm not sure what else I actually need.

Here's the formula for those of you brave enough to enter it in:

'426880×SQRT(10005)/⅀(K=0,2,(6×K)!×(545140134×K+13591409)/((3×K)!×K!^3×(-262537412640768000)^K))'

The funny "⅀" symbol is SUM (RS-SIN) and the "×" is * (multiply) for those of you that don't have fully-working Unicode fonts.

BrickEdit: Changed SQ() to SQRT, as per a later post in this thread. Thanks, Gerson.

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