A certain website has a counter which records the number of hits each day, and keeps a running total. The site gets between 10 and 20 hits, inclusive, per day.
The webmaster noticed that the running total was always prime.
What is the largest number of days the site could be up?
What is the largest number of days if the counter did not start from 1?
clearvars
global firstFew mx mxFew
firstFew=[]; mx=0;
for first=[2 3 5 7 11 13 17]
firstFew=first;
addon
end
function addon()
global firstFew mx mxFew
for new=10:20
if isprime(firstFew(end)+new)
savefirstfew=firstFew;
firstFew(end+1)=firstFew(end)+new;
if length(firstFew)> mx
mx=length(firstFew);
mxFew=firstFew;
end
addon;
firstFew=savefirstfew;
end
end
end
ran very slowly. The farthest I got was 84 (days) long:
2 13 23 37 47 59 71 83 97 107 127 137 149 163 173 191 211 223 233 251 263 277 293 307 317 331 347 359 373 383 397 409 419 431 443 457 467 479 491 503 521 541 557 569 587 599 613 631 641 653 673 683 701 719 733 743 757 769 787 797 809 821 839 853 863 877 887 907 919 929 941 953 967 977 991 1009 1019 1031 1049 1069 1087 1097 1109 1123
based on stopping the program and checking:
K>> fprintf('%5d',mxFew)
2 13 23 37 47 59 71 83 97 107 127 137 149 163 173 191 211 223 233 251 263 277 293 307 317 331 347 359 373 383 397 409 419 431 443 457 467 479 491 503 521 541 557 569 587 599 613 631 641 653 673 683 701 719 733 743 757 769 787 797 809 821 839 853 863 877 887 907 919 929 941 953 967 977 991 1009 1019 1031 1049 1069 1087 1097 1109 1123
K>> disp(length(mxFew))
84
K>>
I'll try a different approach.
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Posted by Charlie
on 2024-06-08 11:57:36 |
some computer findings
