[VA] Short & Sweet Math Challenge #22: April 1st, 2018 Spring Special

[Didier Lachieze]

It took me quite a long time to find the solution to the main course. With my limited knowledge of primality tests I was going nowhere until I took a step back, looked at the overall challenge and started to think to the date of the challenge posting, which led me to Parzival’s Easter Eggs hunt in "Ready Player One", the latest Spielberg movie. At that point I thought: "maybe Valentin has cleverly placed some clues to the solution in the numbers themselves", so I took a different look at the test numbers and bingo, each test number was an Easter egg !

Here is my 42s program for the main course. I managed to squeeze out one byte since yesterday, for a total of 36 bytes.
Usage: XEQ "P", enter the test number, press R/S and see the result.

00 { 36-Byte Prgm }
01▸LBL "P"
02 CLA
03 AON
04 PROMPT
05 AOFF
06 ALENG
07▸LBL 00
08 ATOX
09 10
10 ×
11 ATOX
12 +
13 528
14 -
15 XTOA
16 R↓
17 2
18 -
19 X>0?
20 GTO 00
21 AVIEW
22 END

Here is also a 48-character user function for the HP Prime: sum(CHAR(EXPR(ST(I,2))),I,1,DIM(ST),2)



Usage: provide the input number as a string, e.g. SMC("8082737769637879")

Note: you need first to create the variable ST (for ex. with ST:="") before defining the user function.