A104355 - OEIS

%I #23 Apr 09 2024 09:24:31

%S 0,0,0,0,1,1,1,1,1,2,2,2,2,2,3,3,3,3,3,4,4,4,4,4,4,4,4,4,4,4,4,5,5,5,

%T 5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,6,6,6,6,6,

%U 6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6

%N Number of trailing zeros in decimal representation of A104350(n).

%H Amiram Eldar, <a href="/A104355/b104355.txt">Table of n, a(n) for n = 1..10000</a>

%H David A. Corneth, <a href="/A104355/a104355.gp.txt">PARI link</a>

%H Reinhard Zumkeller, <a href="/A104350/a104350.txt">Products of largest prime factors of numbers <= n</a>.

%F a(A104356(n)) = n and a(m) < n for m < A104356(n);

%F a(n) = A122840(A104350(n)). - _Reinhard Zumkeller_, Mar 10 2013

%t IntegerExponent[FoldList[Times, Array[FactorInteger[#][[-1, 1]] &, 100]], 10] (* _Amiram Eldar_, Apr 08 2024 *)

%o (PARI) gpf(n) = {my(p = factor(n)[, 1]); p[#p];}

%o a(n) = valuation(prod(k = 2, n, gpf(k)), 10); \\ _Amiram Eldar_, Apr 08 2024

%o (PARI) \\ See link. _David A. Corneth_, Apr 08 2024

%Y Cf. A000079, A027868, A080193, A104350, A104356, A122840.

%K nonn,base

%O 1,10

%A _Reinhard Zumkeller_, Mar 06 2005