A181839 Minimum of { k<n | k>0 is strong prime to n}, or zero if this set is empty.

0, 1, 0, 0, 0, 3, 0, 4, 3, 5, 7, 3, 5, 5, 3, 4, 7, 3, 5, 4, 3, 8, 5, 3, 5, 7, 3, 4, 5, 3, 7, 4, 3, 5, 5, 3, 11, 5, 3, 4, 7, 3, 5, 4, 3, 7, 7, 3, 5, 5, 3, 4, 5, 3, 5, 4, 3, 5, 5, 3, 7, 7, 3, 4, 5, 3, 7

Offset

0,6

Comments

k is strong prime to n iff k is coprime to n and k does not divide n-1.

Links

Table of n, a(n) for n=0..66.

Peter Luschny, Strong coprimality.

Example

a(11) = min{3, 4, 6, 7, 8, 9} = 3.

Maple

with(numtheory):
Primes := n -> select(k->isprime(k), {$1..n}):
StrongCoprimes := n -> select(k->igcd(k, n)=1, {$1..n}) minus divisors(n-1):
A181839 := proc(n) min(op(StrongCoprimes(n))); subs(infinity=0, %) end:

Mathematica

a[n_] := Min[ Select[ Range[n-1], CoprimeQ[#, n] && ! Divisible[n-1, #] &] ] /. Infinity -> 0; a[1] = 1; Table[a[n], {n, 0, 66}] (* Jean-François Alcover, Jun 27 2013 *)

Prog

(PARI) a(n)={ for(k=2, n-2, gcd(k, n)==1 & (n-1)%k & return(k)); n==1 }  \\ M. F. Hasler, Nov 17 2010

Crossrefs

Cf. A181830, A181840.

Sequence in context: A072480 A243920 A344905 * A100939 A099925 A351002

Adjacent sequences: A181836 A181837 A181838 * A181840 A181841 A181842

Keyword

nonn

Author

Peter Luschny, Nov 17 2010

Status

approved