A271774 a(1) = 1, then a(n) is the maximum of all 0 < m < n for which a(m) divides n.
1, 1, 2, 3, 2, 5, 2, 7, 4, 7, 2, 11, 2, 13, 6, 13, 2, 17, 2, 19, 10, 19, 2, 23, 6, 23, 4, 27, 2, 29, 2, 31, 12, 31, 10, 33, 2, 37, 16, 37, 2, 41, 2, 43, 6, 43, 2, 47, 10, 49, 18, 47, 2, 53, 12, 53, 22, 53, 2, 59, 2, 61, 10, 61, 16, 61, 2, 67, 26, 67, 2, 71, 2
Offset: 1
Keywords
Examples
a(1) = 1 by definition. a(2) = 1 because a(1) divides 2. a(3) = 2 because a(2) divides 3. a(4) = 3 because a(3) divides 4. a(5) = 2 because a(2) divides 5. a(6) = 5 because a(5) divides 6. a(7) = 2 because a(2) divides 7. a(8) = 7 because a(7) divides 8.
Links
- Robert Israel, Table of n, a(n) for n = 1..10000
Programs
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Maple
A:= proc(n) option remember; local m; for m from n-1 by -1 do if n mod A(m) = 0 then return m fi od end proc: A(1):= 1: seq(A(i),i=1..100); # Robert Israel, Apr 14 2016 -
Mathematica
a[1] = 1; a[n_] := a[n] = Block[{m = n - 1}, While[Mod[n, a[m]] > 0, m--]; m]; Array[a, 100] (* Giovanni Resta, Apr 14 2016 *)
Comments