A298866 - OEIS

%I #6 Apr 17 2018 18:32:22

%S 1,2,3,4,6,8,9,10,12,14,15,16,17,18,20,22,23,24,25,27,28,30,31,32,34,

%T 35,36,37,38,39,42,43,44,45,47,48,49,50,52,54,55,56,58,59,60,61,62,64,

%U 65,66,67,69,70,72,73,74,76,77,78,79,80,83,84,85,86,88

%N Positions of primes p when all p and 4*p are arranged in increasing order.

%H Clark Kimberling, <a href="/A298866/b298866.txt">Table of n, a(n) for n = 1..1000</a>

%e The joint ranking begins with 2,3,5,7,8,11,12,13,17,19,20, as in A298865, so that ranks occupied by primes are 1,2,3,4,6,7,8,10,...

%t z = 200; u = Prime[Range[z]]; w = Take[Union[u, 4 u], z]; (* A298865 *)

%t p[n_] := If[MemberQ[u, w[[n]]], 0, 1];

%t t = Table[p[n], {n, 1, z}];

%t Flatten[Position[t, 0]]  (* A298866 *)

%t Flatten[Position[t, 1]]  (* A298867 *)

%Y Cf. A000040, A298866, A298867 (complement).

%K nonn,easy

%O 1,2

%A _Clark Kimberling_, Apr 14 2018