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A298861
Rank of n-th prime when all the primes and twice-primes are jointly ranked.
2
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
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
KEYWORD
nonn,easy
AUTHOR
Clark Kimberling, Feb 13 2018
STATUS
approved