A298861 Rank of n-th prime when all the primes and twice-primes are jointly ranked.

1, 2, 4, 6, 8, 9, 11, 12, 14, 16, 17, 19, 21, 22, 24, 25, 27, 28, 30, 31, 32, 34, 36, 38, 40, 41, 42, 44, 45, 46, 49, 50, 52, 53, 56, 57, 58, 60, 62, 63, 65, 66, 67, 68, 70, 71, 74, 77, 79, 80, 81, 82, 83, 84, 86, 88, 89, 90, 92, 94, 95, 96, 99, 100, 101

Offset

1,2

Links

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

Example

A001751 = ordered sequence of primes and twice-primes: 2,3,4,5,6,7,10,... in which the primes occupy ranks 1,2,4,6,...

Mathematica

z = 1000; u = Prime[Range[z]]; w = Take[Union[u, 2 u], z];
p[n_] := If[MemberQ[u, w[[n]]], 0, 1];
Take[w, z];  (* A001751 *)
t = Table[p[n], {n, 1, z}];
Flatten[Position[t, 0]];  (* A298861 *)
Flatten[Position[t, 1]];  (* A298862 *)

Crossrefs

Cf. A000040, A001751, A298862 (complement).

Sequence in context: A184012 A186354 A186149 * A114571 A376452 A050091

Adjacent sequences: A298858 A298859 A298860 * A298862 A298863 A298864

Keyword

nonn,easy

Author

Clark Kimberling, Feb 13 2018

Status

approved