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A094540
Last digit of the n-th perfect number.
6
6, 8, 6, 8, 6, 6, 8, 8, 6, 6, 8, 8, 6, 8, 8, 8, 6
OFFSET
1,1
COMMENTS
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
REFERENCES
David Wells, The Penguin Dictionary of Curious and Interesting Numbers. Penguin Books, NY, 1986, Revised edition 1987. See p. 107.
LINKS
Math Forum at Drexel, List of Perfect Numbers.
Eric Weisstein's World of Mathematics, Perfect Number.
MAPLE
# (Maple code from N. J. A. Sloane)
# 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);
MATHEMATICA
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 *)
CROSSREFS
Cf. A000396. See A000043 for the present state of knowledge about Mersenne primes.
Sequence in context: A200326 A088751 A153627 * A010724 A196822 A065356
KEYWORD
nonn,hard,base
AUTHOR
Eric W. Weisstein, May 08 2004
EXTENSIONS
Edited by N. J. A. Sloane, Apr 01 2008, at the suggestion of Ant King and Omar E. Pol
STATUS
approved