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Given the Function, Calculate the Value (Posted on 2023-08-08) Difficulty: 3 of 5
Each of A and B is a positive real number. Consider this function:
         A*B
A o B = -----
         A+B
Determine the value of:

21o(22o(23o ......o(22022 o 22023)))

See The Solution Submitted by K Sengupta    
Rating: 5.0000 (1 votes)

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Solution computer solution | Comment 2 of 4 |
Early on, with lower powers of two, the final (rightmost) power of two is the numerator of the answer, and the denominator is one less than the numerator:

final determined
exp't value
    3 8/7
    4 16/15
    5 32/31
    6 64/63
    7 128/127
    8 256/255
    9 512/511
   10 1024/1023
   11 2048/2047
   12 4096/4095
   13 8192/8191
   14 16384/16383
   15 32768/32767
   16 65536/65535
   17 131072/131071
   18 262144/262143
   19 524288/524287
   20 1048576/1048575
   21 2097152/2097151
   22 4194304/4194303
   23 8388608/8388607
   24 16777216/16777215
   25 33554432/33554431

This continues through extremely large values of both numerator and denominator. At 2^2023 as the rightmost number, you get

9631218335423173696015738454064712512625486454282845268288357683278517
4664461287537804846201905350278880351665383273421210406896920475128576
4221918179043624419894139984279754512017898273159626328827668380262481
2208650177312678026009153751831792643806511654213677735639479033914667
6855708979226348173410849338514606325830049576416536529554633780885267
3629710735621386935094923561594142327134318905856137785813985574356271
6799186944470152944816918493419174323465595015026833030825915850745767
8696308503954644628109504872366923085654833908790992275376288406060765
9880382812905450025751549153093939827557015748608
/
9631218335423173696015738454064712512625486454282845268288357683278517
4664461287537804846201905350278880351665383273421210406896920475128576
4221918179043624419894139984279754512017898273159626328827668380262481
2208650177312678026009153751831792643806511654213677735639479033914667
6855708979226348173410849338514606325830049576416536529554633780885267
3629710735621386935094923561594142327134318905856137785813985574356271
6799186944470152944816918493419174323465595015026833030825915850745767
8696308503954644628109504872366923085654833908790992275376288406060765
9880382812905450025751549153093939827557015748607

The numerator and denominator are each 609 digits long with the latter 1 unit less, so it's quite close to 1.

 
 prod=sym(2)^2023;
 for i=2022:-1:1
   prod=prod*sym(2)^i/(prod+sym(2)^i)
   pr=char(prod)
   disp([i,length(pr),strfind(pr,'/')])
 end
 disp(prod)
disp([i,length(pr),strfind(pr,'/')])

  Posted by Charlie on 2023-08-08 08:46:00
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