A231472 Largest integer less than 12 and coprime to n.

11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 10, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 9, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 10, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 9, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 9, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 7, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 10

Offset: 1

Author

M. F. Hasler, Nov 09 2013

Keywords

• nonn
• easy

Comments

Values in this sequence are 1, 5, 7, 8, 9, 10, and 11; the average value is 3569/330 = 10.81515.... - Charles R Greathouse IV, Aug 19 2016

Examples

			a(1..10)=11 because this is the largest integer less than 12 and it is coprime to n=1,...,10.
a(11)=10 because 11 is not coprime to 11 but 10 is.
a(22)=9 because 11 and 10 are not coprime to 22=2*11.
a(2310)=1 because 2310=2*3*5*7*11 is not coprime to any number n>1, n<12.
		

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A231471 (analog for 11), A231470 (analog for 10), A231155.

Programs

Mathematica

Table[SelectFirst[Range[11,1,-1],CoprimeQ[#,n]&],{n,80}] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Mar 02 2018 *)

PARI

a(n,m=12)=for(k=1,m,gcd(n,m-k)==1&&return(m-k))