A298866 Positions of primes p when all p and 4*p are arranged in increasing order.

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, 35, 36, 37, 38, 39, 42, 43, 44, 45, 47, 48, 49, 50, 52, 54, 55, 56, 58, 59, 60, 61, 62, 64, 65, 66, 67, 69, 70, 72, 73, 74, 76, 77, 78, 79, 80, 83, 84, 85, 86, 88

Offset: 1

Author

Clark Kimberling, Apr 14 2018

Keywords

• nonn
• easy

Examples

			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,...
		

Links

• Clark Kimberling, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A000040, A298866, A298867 (complement).

Programs

Mathematica

z = 200; u = Prime[Range[z]]; w = Take[Union[u, 4 u], z]; (* A298865 *)
p[n_] := If[MemberQ[u, w[[n]]], 0, 1];
t = Table[p[n], {n, 1, z}];
Flatten[Position[t, 0]]  (* A298866 *)
Flatten[Position[t, 1]]  (* A298867 *)