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A094540
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Last digit of the n-th perfect number.
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6
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6, 8, 6, 8, 6, 6, 8, 8, 6, 6, 8, 8, 6, 8, 8, 8, 6
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,1
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COMMENTS
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Conjecture: Ratio of 6's to 8's approaches 1.5 as a limit as this sequence approaches infinity. - J. Lowell, Jun 26 2007
Since the best known lower bound for odd perfect numbers is ca. 10^1500, I removed all terms after a(17). - Ivan Panchenko, Sep 16 2014
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LINKS
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MAPLE
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# let s1 := list of terms in A000043
f:=n->if n mod 4 = 0 then 4 else n mod 4; fi; g:= x->2^f(x-1)*(2^f(x)-1); map(g, s1);
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MATHEMATICA
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p={ the list of the Mersenne exponents (A000043) }; Mod[(PowerMod[2, p, 10] - 1)(PowerMod[2, p - 1, 10]), 10] (* Robert G. Wilson v, May 23 2004 *)
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CROSSREFS
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Cf. A000396. See A000043 for the present state of knowledge about Mersenne primes.
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KEYWORD
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nonn,hard,base
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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