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Record values in A040081.
7

%I #11 Dec 20 2018 12:43:54

%S 2,3,4,7,12,23,25,2551,800516

%N Record values in A040081.

%C A040081(659) not yet found. The index sequence of this one is 1, 13, 23, 43, 59, 88, 127, 148, 659.

%C 800516 was found by Dave Linton in 2004.

%H Ray Ballinger and Wilfrid Keller, <a href="http://www.prothsearch.com/rieselprob.html">Riesel Problem</a>

%e A040081(1)=2; A040081(13)=3; A040081(659)>8192

%t kmax=8192; k = 0; n = 0; km = k; While[k < kmax, n++; k = 0; cp = n*(2^k) - 1; While[(!PrimeQ[cp]) && (k < kmax), k++; cp = n*(2^k) - 1]; If[k > km, km = k; Print[{n, km}]]]

%Y Cf. A038699, A040081, A240113.

%K nonn,more

%O 1,1

%A _Lei Zhou_, Feb 24 2005

%E Edited by _T. D. Noe_, Nov 15 2010