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Old 2021-08-18, 04:27   #6
sweety439
 
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"99(4^34019)99 palind"
Nov 2016
(P^81993)SZ base 36

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To check whether a number n>1 is untouchable, checking to (n-1)^2 is enough, if no k<=(n-1)^2 is found that sigma(k)-k = n, then n is untouchable.
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