A225017 - OEIS

%I #19 Oct 27 2023 22:11:46

%S 1,1,7,1,13,11,19,23,1,13,1,19,7,23,17,11,29,7,1,59,61,31,67,37,41,77,

%T 79,89,17,83,91,13,53,89,103,23,109,13,31,67,13,137,29,149,151,29,7,1,

%U 29,79,151,19,13,119,127,167,49,43,211,191,199,97,187,17,83

%N Odd part of digit sum of 5^n divided by maximal possible power of 5.

%C Does the sequence contain every prime greater than 5?

%H Alois P. Heinz, <a href="/A225017/b225017.txt">Table of n, a(n) for n = 0..10000</a> (terms n = 0..999 from Peter J. C. Moses)

%F a(n) = A132740(A055566(n)). - _Michel Marcus_, Dec 10 2018

%p a:= proc(n) local m, r; m, r:= 0, 5^n;

%p       while r>0 do m:= m+irem(r, 10, 'r') od;

%p       while irem(m, 2, 'r')=0 do m:=r od;

%p       while irem(m, 5, 'r')=0 do m:=r od; m

%p     end:

%p seq(a(n), n=0..80);  # _Alois P. Heinz_, Apr 24 2013

%t Map[#/(2^IntegerExponent[#,2] 5^IntegerExponent[#,5])&[Total[ IntegerDigits[5^#]]]&,Range[0,99]] (* _Peter J. C. Moses_, Apr 24 2013 *)

%o (PARI) a(n) = my(x = sumdigits(5^n)); x/5^valuation(x, 5) >> valuation(x, 2); \\ _Michel Marcus_, Dec 10 2018

%Y Cf. A055566, A132740.

%K nonn,base

%O 0,3

%A _Vladimir Shevelev_, Apr 24 2013