A097099 - OEIS

%I #26 Jul 14 2015 23:21:45

%S 1,1,1,1,2,6,1,1,2,3,12,1,2,22,2,4,13,12,6,1,4,1,4,9,2,9,5,6,2,1,9,17,

%T 22,7,19,73,23,12,5,27,33,64,33,5,7,41,44,35,29,3,19,6,26,5,11,9,33,

%U 34,16,63,46,8,4,24,48,32,11,29,26,6,25,17,31,6,46,33,46,17,8,61,12,23,76

%N Smallest k>0 such that (2^k)*A002110(n) - 1 is prime.

%H Pierre CAMI, <a href="/A097099/b097099.txt">Table of n, a(n) for n = 1..1042</a>

%t f[n_] := Block[{k = 1, p = Product[Prime[i], {i, n}]}, While[ !PrimeQ[2^k*p - 1], k++ ]; k]; Table[ f[n], {n, 83}] (* _Robert G. Wilson v_, Sep 27 2004 *)

%t kp[n_]:=Module[{k=1},While[!PrimeQ[2^k n-1],k++];k]; With[{prmrls=Rest[ FoldList[Times,1,Prime[Range[90]]]]},kp/@prmrls] (* _Harvey P. Dale_, Feb 01 2012 *)

%o (PFGW & SCRIPT)

%o Command pfgw64 -f in.txt

%o in.txt file = SCRIPT file

%o SCRIPT

%o DIM n,0

%o DIM i,0

%o DIM pp

%o DIMS t

%o OPENFILEOUT myf,a(n).txt

%o LABEL loop1

%o SET n,n+1

%o SET i,0

%o LABEL loop2

%o SET i,i+1

%o SETS t,%d,%d,%d\,;n;p(n);i

%o SET pp,(2^i)*p(n)#-1

%o PRP pp,t

%o IF ISPRP THEN GOTO a

%o GOTO loop2

%o LABEL a

%o WRITE myf,t

%o GOTO loop1

%Y Cf. A002110, A098929.

%K nonn

%O 1,5

%A _Pierre CAMI_, Sep 15 2004

%E More terms from _Robert G. Wilson v_, Sep 27 2004