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%I #15 Jul 25 2020 10:39:02
%S 2,1,1,1,3,1,2,1,1,1,3,1,2,1,1,1,3,1,2,1,1,1,3,1,2,1,1,1,3,1,2,1,1,1,
%T 4,1,2,1,1,1,3,1,2,1,1,1,3,1,2,1,1,1,3,1,2,1,1,1,3,1,2,1,1,1,3,1,2,1,
%U 1,1,3,1,2,1,1,1,3,1,2,1,1,1,3,1,2,1,1,1,3,1,2,1,1,1,3,1,2,1,1,1
%N a(n) = the number of terms in row n of A175306.
%C a(2n) = 1, and a(3n)=1, for all positive integers n.
%H Robert Israel, <a href="/A175307/b175307.txt">Table of n, a(n) for n = 1..10000</a>
%p A175307:=proc(n)
%p local R,last,k,P;
%p R:= n;
%p last:= n;
%p P:= n;
%p while igcd(last,6)=1 do
%p for k from last+1 do
%p if igcd(k-1,P) = 1 and igcd(k,P) = 1 and igcd(k+1,P) =1 then
%p R:= R, k; last:= k; P:= P*k; break
%p fi
%p od
%p od;
%p nops([R])
%p end proc:
%p map(A175307, [$1..100]); # _Robert Israel_, Feb 10 2017
%t 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];
%t a[n_] := Length[row[n]];
%t Array[a, 100] (* _Jean-François Alcover_, Jul 25 2020, after _Robert Israel_ *)
%Y Cf. A175306
%K nonn
%O 1,1
%A _Leroy Quet_, Mar 26 2010
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