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A298862 Rank of n-th twice-prime when all the primes and twice-primes are jointly ranked. 2
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 (list; graph; refs; listen; history; text; internal format)
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: A075782 A050090 A152004 * A198409 A330072 A213510

Adjacent sequences:  A298859 A298860 A298861 * A298863 A298864 A298865

KEYWORD

nonn,easy

AUTHOR

Clark Kimberling, Feb 13 2018

STATUS

approved

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Last modified April 10 20:20 EDT 2021. Contains 342856 sequences. (Running on oeis4.)