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A337723 a(n) = prime(n-2) - ceiling(a(n-2)/2); a(1)=0, a(2)=1. 1
0, 1, 2, 2, 4, 6, 9, 10, 12, 14, 17, 22, 22, 26, 30, 30, 32, 38, 43, 42, 45, 50, 50, 54, 58, 62, 68, 70, 69, 72, 74, 77, 90, 92, 92, 93, 103, 104, 105, 111, 114, 117, 122, 122, 130, 132, 132, 133, 145, 156, 154, 151, 156, 163, 163, 169, 175, 178, 181, 182, 186, 190, 190 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Table of n, a(n) for n=1..63.

EXAMPLE

a(3) = prime(1) - ceiling(a(1)/2) =  2 - ceiling(0/2) = 2,

a(4) = prime(2) - ceiling(a(2)/2) =  3 - ceiling(1/2) = 2,

a(5) = prime(3) - ceiling(a(3)/2) =  5 - ceiling(2/2) = 4,

a(6) = prime(4) - ceiling(a(4)/2) =  7 - ceiling(2/2) = 6,

a(7) = prime(5) - ceiling(a(5)/2) = 11 - ceiling(4/2) = 9.

MATHEMATICA

a[1] = 0; a[2] = 1; a[n_] := a[n] = Floor[(2*Prime[n - 2] - a[n - 2])/2]; Array[a, 100] (* Amiram Eldar, Sep 18 2020 *)

PROG

(Ruby) require 'prime'

values = [0, 1]

Prime.each(100) do |prime|

    values << prime - (values[-2]+1) / 2

end

p values

(PARI) a(n) = if (n<=2, n-1, prime(n-2) - ceil(a(n-2)/2)); \\ Michel Marcus, Oct 07 2020

CROSSREFS

Cf. A000040. Similar to A337724 with ceiling instead of floor.

Sequence in context: A091966 A231187 A055529 * A222735 A299408 A338937

Adjacent sequences:  A337720 A337721 A337722 * A337724 A337725 A337726

KEYWORD

nonn

AUTHOR

Simon Strandgaard, Sep 17 2020

STATUS

approved

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Last modified September 27 11:29 EDT 2021. Contains 347689 sequences. (Running on oeis4.)