OFFSET
1,1
COMMENTS
a(2n) = 1, and a(3n)=1, for all positive integers n.
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
MAPLE
A175307:=proc(n)
local R, last, k, P;
R:= n;
last:= n;
P:= n;
while igcd(last, 6)=1 do
for k from last+1 do
if igcd(k-1, P) = 1 and igcd(k, P) = 1 and igcd(k+1, P) =1 then
R:= R, k; last:= k; P:= P*k; break
fi
od
od;
nops([R])
end proc:
map(A175307, [$1..100]); # Robert Israel, Feb 10 2017
MATHEMATICA
row[n_] := Module[{R = {n}, last = n, k, P = n}, While[GCD[last, 6] == 1, For[k = last + 1, True, k++, If[GCD[k - 1, P] == 1 && GCD[k, P] == 1 && GCD[k + 1, P] == 1, AppendTo[R, k]; last = k; P = P k; Break[]]]]; R];
a[n_] := Length[row[n]];
Array[a, 100] (* Jean-François Alcover, Jul 25 2020, after Robert Israel *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Leroy Quet, Mar 26 2010
STATUS
approved