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A181863
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Decimal sturdy primes: primes p such that sum of digits of k*p for any positive integer k is at least the sum of digits of p.
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3
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OFFSET
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1,1
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COMMENTS
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Contains prime repunits A004022 as a subsequence.
For all x>log_10(p), 1+A007953(p-(10^x mod p)) >= A007953(p). This follows from the fact that 10^x+p-(10^x mod p) is a multiple of p.
a(5) > 2*10^11. See a181863_2e11.txt for more details. (End)
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LINKS
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Trevor Clokie, Thomas F. Lidbetter, Antonio Molina Lovett, Jeffrey Shallit, and Leon Witzman, Computational Aspects of Sturdy and Flimsy Numbers, Theoretical Computer Science, Vol. 927 (2022), pp. 65-86; arXiv preprint, arXiv:2002.02731 [cs.DS], 2020.
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CROSSREFS
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KEYWORD
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nonn,base,more,hard
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AUTHOR
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STATUS
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approved
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