A352962 a(1) = 2, a(n) = Min(n,a(n-1)) if gcd(n,a(n-1)) = 1, else a(n) = n + 2.

2, 4, 3, 3, 3, 8, 7, 7, 7, 7, 7, 7, 7, 16, 15, 15, 15, 20, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 40, 39, 39, 39, 44, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43

Offset

1,1

Links

Table of n, a(n) for n=1..82.

Example

a(1) = 2, gcd(2,2) = 2 thus a(2) = 4
a(2) = 4, gcd(3,4) = 1 thus a(3) = Min(3,4) = 3
a(3) = 3, gcd(4,3) = 1 thus a(4) = Min(4,3) = 3, etc.

Mathematica

a[1] = 2; a[n_] := a[n] = If[CoprimeQ[n, a[n - 1]], Min[n, a[n - 1]], n + 2]; Array[a, 100] (* Amiram Eldar, Apr 11 2022 *)

Prog

(Python)
from math import gcd
from itertools import count, islice
def A352962_gen(): # generator of terms
    a = 2
    yield a
    for n in count(2):
        yield (a:= min(n, a) if gcd(n, a) == 1 else n+2)
A352962_list = list(islice(A352962_gen(), 30)) # Chai Wah Wu, May 24 2022

Crossrefs

Cf. A000040, A201854.

Sequence in context: A220080 A343766 A299920 * A137363 A110549 A174574

Adjacent sequences: A352959 A352960 A352961 * A352963 A352964 A352965

Keyword

nonn

Author

Ctibor O. Zizka, Apr 11 2022

Status

approved