A054576 Largest proper factor of the largest proper factor of n.

1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 3, 1, 1, 1, 4, 1, 3, 1, 5, 1, 1, 1, 6, 1, 1, 3, 7, 1, 5, 1, 8, 1, 1, 1, 9, 1, 1, 1, 10, 1, 7, 1, 11, 5, 1, 1, 12, 1, 5, 1, 13, 1, 9, 1, 14, 1, 1, 1, 15, 1, 1, 7, 16, 1, 11, 1, 17, 1, 7, 1, 18, 1, 1, 5, 19, 1, 13, 1, 20, 9, 1, 1, 21, 1, 1, 1, 22, 1, 15, 1, 23, 1, 1, 1, 24

Offset

1,8

Comments

Here a "proper factor of n" means 1 if n = 1, and otherwise any d that divides n with 1 <= d < n. - N. J. A. Sloane, Dec 26 2022

Links

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

Formula

a(n) = A053598(A053598(n))

a(n) = A032742(A032742(n)); A117357(n) = A020639(a(n)); A117358(n) = A032742(a(n)) = a(n) / A117357(n); a(A037143(n)) = 1, a(A033942(n)) > 1. - Reinhard Zumkeller, Mar 10 2006

Example

The largest proper factor of 8 is 4, the largest proper factor of 4 is 2, so a(8) = 2. - N. J. A. Sloane, Dec 26 2022

Prog

(Haskell) a054576 = a032742 . a032742  -- Reinhard Zumkeller, Jan 31 2015
(PARI) A054576(n)=A032742(A032742(n)) \\ M. F. Hasler, Apr 03 2017

Crossrefs

Cf. A053598.

Cf. A020639, A032742, A033942, A037143, A117357, A117358.

Sequence in context: A140886 A001492 A347049 * A326840 A326153 A199515

Adjacent sequences: A054573 A054574 A054575 * A054577 A054578 A054579

Keyword

easy,nonn

Author

Henry Bottomley, Apr 11 2000

Extensions

Deleted an incorrect comment and link. - N. J. A. Sloane, Dec 26 2022

Status

approved