A117358 a(n) = A032742(A032742(A032742(n))) = ((n/lpf(n))/lpf(n/lpf(n)))/lpf((n/lpf(n))/lpf(n/lpf(n))), where lpf=A020639, least prime factor.

1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 4, 1, 1, 1, 3, 1, 1, 1, 5, 1, 1, 1, 1, 1, 1, 1, 6, 1, 1, 1, 1, 1, 3, 1, 7, 1, 1, 1, 5, 1, 1, 1, 8, 1, 1, 1, 1, 1, 1, 1, 9, 1, 1, 1, 1, 1, 1, 1, 10, 3, 1, 1, 7, 1, 1, 1, 11, 1, 5, 1, 1, 1, 1, 1, 12, 1, 1, 1, 5, 1, 1, 1

Offset

1,16

Links

Antti Karttunen, Table of n, a(n) for n = 1..65537

Eric Weisstein's World of Mathematics, Least Prime Factor

Formula

a(n) = A032742(A032742(A032742(n))) = A032742(A054576(n)) = A054576(n)/A115561(n).

a(A037144(n)) = 1, a(A033987(n)) > 1.

Mathematica

f[n_] := n/FactorInteger[n][[1, 1]]; (* f is A032742 *)
a[n_] := f@ f@ f@ n;
Array[a, 100] (* Jean-François Alcover, Dec 09 2021 *)
Table[Nest[#/FactorInteger[#][[1, 1]]&, n, 3], {n, 110}] (* Harvey P. Dale, Oct 10 2024 *)

Prog

(Scheme) (define (A117358 n) (A032742 (A032742 (A032742 n)))) ;; Antti Karttunen, Dec 07 2017

Crossrefs

Cf. A014673, A032742, A037144, A033987, A054576, A115561.

Sequence in context: A190867 A355936 A326976 * A294333 A321125 A205617

Adjacent sequences: A117355 A117356 A117357 * A117359 A117360 A117361

Keyword

nonn

Author

Reinhard Zumkeller, Mar 10 2006

Status

approved