%I A093348
%S A093348 0,1,0,1,0,5,4,5,4,5,0,1,0,1,0,5,4,5,4,5,0,1,0,1,0,25,24,25,24,25,20,21,
%T A093348 20,21,20,25,24,25,24,25,20,21,20,21,20,25,24,25,24,25,0,1,0,1,0,5,4,5,
%U A093348 4,5,0,1,0,1,0,5,4,5,4,5,0,1,0,1,0,25,24,25,24,25,20,21,20,21,20,25,24
%N A093348 A 5-fractal "castle" starting with 0.
%H A093348 B. Cloitre, <a href="http://ns3131.ovh.net/~pi314/temporaires/benoit/
               chateau_pentafractal_25.JPG">Graph of a(n) for n=1 up to 25</a>
%H A093348 B. Cloitre, <a href="http://ns3131.ovh.net/~pi314/temporaires/benoit/
               chateau_pentafractal_125.JPG">Graph of a(n) for n=1 up to 125</a>
%H A093348 B. Cloitre, <a href="http://ns3131.ovh.net/~pi314/temporaires/benoit/
               chateau_pentafractal_625.JPG">Graph of a(n) for n=1 up to 625</a>
%F A093348 a(1)=0 then a(n)=w(n)-a(n-w(n)) where w(n)=5^floor(log(n-1)/log(5))
%F A093348 a(n) = sum(i=1, n-1, (-1)^(i-1)*5^valuation(i, 5))
%o A093348 (PARI) a(n)=if(n<2,0,5^floor(log(n-1)/log(5))-a(n-5^floor(log(n-1)/log(5))))
%Y A093348 Cf. A093347, A093349
%Y A093348 Cf. A060904.
%Y A093348 Sequence in context: A131291 A131369 A122219 this_sequence A001050 A113784 
               A021651
%Y A093348 Adjacent sequences: A093345 A093346 A093347 this_sequence A093349 A093350 
               A093351
%K A093348 nonn
%O A093348 1,6
%A A093348 Benoit Cloitre (benoit7848c(AT)orange.fr), Apr 26 2004