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

1,2

Links

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

Example

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,...

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 *)

Crossrefs

Cf. A000040, A298866, A298867 (complement).

Sequence in context: A125292 A101513 A153276 * A108408 A173905 A171581

Adjacent sequences: A298863 A298864 A298865 * A298867 A298868 A298869

Keyword

nonn,easy

Author

Clark Kimberling, Apr 14 2018

Status

approved