A298862 Rank of n-th twice-prime when all the primes and twice-primes are jointly ranked.

3, 5, 7, 10, 13, 15, 18, 20, 23, 26, 29, 33, 35, 37, 39, 43, 47, 48, 51, 54, 55, 59, 61, 64, 69, 72, 73, 75, 76, 78, 85, 87, 91, 93, 97, 98, 102, 104, 106, 108, 112, 114, 118, 120, 122, 124, 129, 134, 136, 138, 141, 143, 145, 149, 152, 155, 156, 158, 160

Offset

1,1

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 twice-primes occupy ranks 3,5,7,...

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, A298861 (complement).

Sequence in context: A050090 A152004 A376453 * A198409 A330072 A213510

Adjacent sequences: A298859 A298860 A298861 * A298863 A298864 A298865

Keyword

nonn,easy

Author

Clark Kimberling, Feb 13 2018

Status

approved