A243291 Difference between n and the index of its largest prime factor: a(n) = n - A061395(n).

1, 1, 1, 3, 2, 4, 3, 7, 7, 7, 6, 10, 7, 10, 12, 15, 10, 16, 11, 17, 17, 17, 14, 22, 22, 20, 25, 24, 19, 27, 20, 31, 28, 27, 31, 34, 25, 30, 33, 37, 28, 38, 29, 39, 42, 37, 32, 46, 45, 47, 44, 46, 37, 52, 50, 52, 49, 48, 42, 57, 43, 51, 59, 63, 59, 61, 48, 61, 60

Offset: 1

Author

Antti Karttunen, Jun 04 2014

Keywords

• nonn

Comments

All terms are strictly positive because A006530(n) <= n, A049084(n) < n and thus A061395(n) < n. [As A061395(n) = A049084(A006530(n))].

Please see also the comments at A243289.

Links

• Antti Karttunen, Table of n, a(n) for n = 1..8192

Crossrefs

Cf. A006530, A049084, A061395, A243289, A243290.

Programs

Mathematica

a[n_] := n - PrimePi[FactorInteger[n][[-1, 1]]]; Array[a, 100] (* Amiram Eldar, Mar 04 2024 *)

Scheme

(define (A243291 n) (- n (A061395 n)))

Formula

a(n) = n - A061395(n).

For n > 1, a(2^n) = (2^n)-1.