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 A175307 a(n) = the number of terms in row n of A175306. 2
 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, 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, 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 (list; graph; refs; listen; history; text; internal format)
 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 Cf. A175306 Sequence in context: A276949 A205794 A241665 * A324825 A316557 A032436 Adjacent sequences:  A175304 A175305 A175306 * A175308 A175309 A175310 KEYWORD nonn AUTHOR Leroy Quet, Mar 26 2010 STATUS approved

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Last modified June 22 12:56 EDT 2021. Contains 345380 sequences. (Running on oeis4.)