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A102630 Numbers n such that no positive number of the form prime(n)-2^k is prime. 1

%I #6 Mar 14 2015 16:50:55

%S 1,2,31,35,54,67,68,74,97,109,126,134,140,151,155,165,168,171,181,205,

%T 244,251,256,260,274,275,276,285,298,328,330,341,352,368,376,389,405,

%U 413,417,421,430,444,447,450,451,463,471,481,495,509,510,516,522,526

%N Numbers n such that no positive number of the form prime(n)-2^k is prime.

%C Large primes tested by Primo.

%H Lei Zhou, <a href="http://www.bme.emory.edu/~lzhou/prime/">Between 2^n and primes</a>.

%e Prime(1)=2, 2-2^0=1, not prime.

%e Prime(31)=127, 127-2^0 through 127-2^6 are nonprime.

%t fQ[n_] := Block[{k = Floor[ Log[2, Prime[n]]], p = Prime[n]}, While[k > -1 && !PrimeQ[p - 2^k], k-- ]; If[k > 0, True, False]]; Select[ Range[ 536], !fQ[ # ] &] (* _Robert G. Wilson v_, Jan 24 2005 *)

%Y Cf. A094076, A102631-A102633.

%K nonn

%O 1,2

%A _Lei Zhou_, Jan 20 2005

%E More terms from _Robert G. Wilson v_, Jan 24 2005

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Last modified March 28 10:55 EDT 2024. Contains 371241 sequences. (Running on oeis4.)