A064741 - OEIS

%I #19 May 26 2018 21:14:36

%S 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,

%T 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,

%U 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

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

%H Antti Karttunen, <a href="/A064741/b064741.txt">Table of n, a(n) for n = 1..65539</a>

%H <a href="/index/Ed#EKG">Index entries for sequences related to EKG sequence</a>

%F a(n) = A061395(A064413(n)) = A000720(A304733(n)). - _Antti Karttunen_, May 18 2018

%t 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 *)

%o (PARI)

%o A061395(n) = if(n>1, primepi(vecmax(factor(n)[, 1])), 0);

%o A064741(n) = A061395(A064413(n)); \\ Needs also code for A064413.

%Y Length of n-th row of table in A064744.

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

%K nonn

%O 1,4

%A _N. J. A. Sloane_, Oct 18 2001

%E 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