A337823 a(n) = prime(n-1) - floor(a(n-1)/2); a(1)=1.

1, 2, 2, 4, 5, 9, 9, 13, 13, 17, 21, 21, 27, 28, 29, 33, 37, 41, 41, 47, 48, 49, 55, 56, 61, 67, 68, 69, 73, 73, 77, 89, 87, 94, 92, 103, 100, 107, 110, 112, 117, 121, 121, 131, 128, 133, 133, 145, 151, 152, 153, 157, 161, 161, 171, 172, 177, 181, 181, 187

Offset

1,2

Links

Table of n, a(n) for n=1..60.

Example

a(2) = prime(1) - floor(a(1)/2) =  2 - floor(1/2) = 2,
a(3) = prime(2) - floor(a(2)/2) =  3 - floor(2/2) = 2,
a(4) = prime(3) - floor(a(3)/2) =  5 - floor(2/2) = 4,
a(5) = prime(4) - floor(a(4)/2) =  7 - floor(4/2) = 5,
a(6) = prime(5) - floor(a(5)/2) = 11 - floor(5/2) = 9.

Mathematica

a[1] = 1; a[n_] := a[n] = Prime[n - 1] - Floor[a[n - 1]/2]; Array[a, 100] (* Amiram Eldar, Sep 24 2020 *)

Prog

(Ruby) require 'prime'
values = [1]
Prime.each(100) { |prime| values << prime - values[-1] / 2 }
p values
(PARI) a(n) = if (n<=2, n, prime(n-1) - floor(a(n-1)/2)); \\ Michel Marcus, Oct 07 2020; corrected Jun 13 2022

Crossrefs

Cf. A000040. Similar to A337724 that has step size 2, instead of 1 here.

Sequence in context: A085570 A059850 A308906 * A051630 A050045 A308955

Adjacent sequences: A337820 A337821 A337822 * A337824 A337825 A337826

Keyword

nonn

Author

Simon Strandgaard, Sep 24 2020

Status

approved