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A181839
Minimum of { k<n | k>0 is strong prime to n}, or zero if this set is empty.
2
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.
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
Sequence in context: A072480 A243920 A344905 * A100939 A099925 A351002
KEYWORD
nonn
AUTHOR
Peter Luschny, Nov 17 2010
STATUS
approved