|
%I #7 Jul 31 2017 03:23:59
%S 20,22,36,48,78,90,132,162,258,330,372,468,498,510,678,708,720,750,
%T 762,888,918,972,1098,1170,1212,1380,1560,1602,1758,1800,1980,2052,
%U 2178,2220,2358,2442,2472,2610,2682,2778,2862
%N Numbers such that the two adjacent integers are a prime and 7 times a prime.
%H G. C. Greubel, <a href="/A163630/b163630.txt">Table of n, a(n) for n = 1..5000</a>
%e a(2)=22 lies between 21=7*A000040(2) and 23=A000040(9).
%e a(3)=36 lies between 35=7*A000040(3) and 37=A000040(12).
%t prQ[n_] := Module[{a = n - 1, b = n + 1}, (PrimeQ[a] && PrimeQ[b/7]) || (PrimeQ[b] && PrimeQ[a/7])]; Select[Range[5000], prQ] (* _G. C. Greubel_, Jul 30 2017 *)
%Y Cf. A000040, A163492.
%K nonn
%O 1,1
%A _Juri-Stepan Gerasimov_, Aug 02 2009
%E 20 inserted, 62 removed, 90 added etc. by _R. J. Mathar_, Aug 07 2009
|
