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A138876 First 3 digits of n-th even perfect number.

%I A138876 #30 Aug 23 2018 16:58:02
%S A138876 6,28,496,812,335,858,137,230,265,191,131,144,235,141,541,108,994,335,
%T A138876 182,407,114,598,395,931,100,811,365,144,136,131,278,151,838,849,331,
%U A138876 194,811,955,427,793,448,746,497,775,204,144,500
%N A138876 First 3 digits of n-th even perfect number.
%C A138876 As of August 6, 2018, GIMPS reports that all Mersenne primes through the 47th have been positively identified, i.e., that there are no further such primes below the 47th.  Thus, the sequence through a(47), i.e., through the term 500, is complete.  Additional terms (169, 451, 109) are correct but it is still possible that more terms may be found above a(47) but below a(50). [_Harvey P. Dale_, Jul 17 2011] [Updated by _Ivan Panchenko_, Aug 06 2018]
%H A138876 Jan Munch Pedersen, <a href="https://web.archive.org/web/20141006120722/http://amicable.homepage.dk/perfect.htm">Known Perfect Numbers</a> [From Steven Bi (chenhsi(AT)stanford.edu), Jan 18 2009] [Replaced with Wayback Machine link by _Felix Fröhlich_, Aug 04 2018]
%H A138876 Omar E. Pol, <a href="http://www.polprimos.com/#Los%20n%C3%BAmeros%20perfectos">Los numeros perfectos</a>
%t A138876 f[n_] := Block[{e, p, mpe = MersennePrimeExponent@ n}, p = (2^mpe - 1) 2^(mpe - 1); e = IntegerLength@ p - 3; If[e < 1, p, Quotient[p, 10^e]]]; Array[f, 44] (* _Robert G. Wilson v_, Aug 06 2018 *)
%Y A138876 Cf. A000396, A135617, A138864, A138873, A138877.
%Y A138876 First three digits of each term from A138877. [Steven Bi (chenhsi(AT)stanford.edu), Jan 18 2009]
%K A138876 base,more,nonn
%O A138876 1,1
%A A138876 _Omar E. Pol_, Apr 02 2008
%E A138876 a(15)-a(31) added by Steven Bi (chenhsi(AT)stanford.edu), Jan 18 2009
%E A138876 Corrected a(27) and added a(32) through a(40) by _Harvey P. Dale_, Jul 17 2011
%E A138876 Definition changed (inserting the word "even") and a(41)-a(47) added by _Ivan Panchenko_, Aug 04 2018