A298867 Positions of numbers 4*p when all primes p and products 4*p are arranged in increasing order.

5, 7, 11, 13, 19, 21, 26, 29, 33, 40, 41, 46, 51, 53, 57, 63, 68, 71, 75, 81, 82, 87, 90, 95, 101, 105, 107, 110, 113, 117, 127, 131, 134, 135, 143, 146, 151, 156, 160, 165, 168, 170, 178, 180, 183, 184, 193, 202, 204, 206, 209, 214, 215, 222, 227, 233, 237

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 products 4*p are 5,7,11,...
		

Links

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

Crossrefs

Cf. A000040, A298866, A298866 (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 *)