A064741 Length of A064743(n); Index of the largest prime factor of the n-th term of EKG-sequence.

0, 1, 1, 2, 2, 2, 2, 1, 3, 3, 3, 2, 4, 4, 4, 2, 1, 3, 5, 5, 5, 2, 3, 3, 4, 4, 6, 6, 6, 2, 1, 7, 7, 7, 4, 8, 8, 8, 3, 3, 5, 9, 9, 9, 2, 3, 6, 2, 4, 4, 4, 3, 5, 6, 4, 10, 10, 10, 5, 11, 11, 11, 2, 1, 7, 12, 12, 12, 3, 6, 8, 3, 13, 13, 13, 2, 4, 5, 5, 14, 14, 14, 3, 7, 8, 3, 9, 15, 15, 15, 2, 4, 6, 6, 7, 5, 4, 2, 16, 16, 16, 8, 5, 4, 10

Offset: 1

Author

N. J. A. Sloane, Oct 18 2001

Keywords

• nonn

Links

• Antti Karttunen, Table of n, a(n) for n = 1..65539
• Index entries for sequences related to EKG sequence

Crossrefs

Length of n-th row of table in A064744.

Cf. A061395, A064413, A304733, A304734 (ordinal transform).

Programs

Mathematica

PrimePi@ FactorInteger[#][[-1, 1]] & /@ Nest[Append[#, Block[{k = 3}, While[Or[MemberQ[#, k], GCD[#[[-1]], k] == 1], k++]; k]] &, {1, 2}, 103] (* Michael De Vlieger, May 22 2018 *)

PARI

A061395(n) = if(n>1, primepi(vecmax(factor(n)[, 1])), 0);
A064741(n) = A061395(A064413(n)); \\ Needs also code for A064413.

Formula

a(n) = A061395(A064413(n)) = A000720(A304733(n)). - Antti Karttunen, May 18 2018

Extensions

Offset corrected to 1, terms a(42) .. a(46) [that were terms a(41) .. a(45)] also corrected, more terms and alternative description added by Antti Karttunen, May 18 2018