A191112 -id:A191112 - cp's OEIS frontend

A190911 Least number coprime to n and n+3.

3, 3, 5, 3, 3, 5, 3, 3, 5, 3, 3, 7, 3, 3, 7, 3, 3, 5, 3, 3, 5, 3, 3, 5, 3, 3, 7, 3, 3, 7, 3, 3, 5, 3, 3, 5, 3, 3, 5, 3, 3, 11, 3, 3, 7, 3, 3, 5, 3, 3, 5, 3, 3, 5, 3, 3, 7, 3, 3, 11, 3, 3, 5, 3, 3, 5, 3, 3, 5, 3, 3, 7, 3, 3, 7, 3, 3, 5, 3, 3, 5, 3, 3, 5, 3, 3

Offset: 1

Jonathan Vos Post, May 26 2011

This is to n+3 as A053670 is to n+1. This is the 3rd row of the array A(k,n) = Least number coprime to n and n+k where A053670 is the 1st row. First n for which a(n) = (3, 5, 7, 11, 13, 17, 19, ...) are A191112 = (1, 3, 12, 42, 165, 3000, 2142, ...).

			a(12) = 7 because the prime factors of 12 and 12+3 = 15 are {2, 3, 5} and the next available prime is 7.

Nathaniel Johnston, Table of n, a(n) for n = 1..10000

Cf. A053669-A053674, A191112.

A190911 := proc(n) local k: for k from 3 by 2 do if(gcd(k,n)=1 and gcd(k,n+3)=1)then return k: fi: od: end: seq(A190911(n),n=1..100); # Nathaniel Johnston, May 26 2011

a(15) corrected by Nathaniel Johnston, May 26 2011

cp's OEIS Frontend

A190911 Least number coprime to n and n+3.

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