Search: id:A007091
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%I A007091 M0595
%S A007091 0,1,2,3,4,10,11,12,13,14,20,21,22,23,24,30,31,32,33,34,40,41,42,43,44,
%T A007091 100,101,102,103,104,110,111,112,113,114,120,121,122,123,124,130,131,
%U A007091 132,133,134,140,141,142,143,144,200,201,202,203,204,210,211,212,213
%N A007091 Numbers in base 5.
%C A007091 Contribution from Rick L. Shepherd (rshepherd2(AT)hotmail.com), Jun 25 
               2009: (Start)
%C A007091 Nonnegative integers with no decimal digit > 4.
%C A007091 Thus nonnegative integers in base 10 whose doubling by normal addition 
               or multiplication requires no carry operation. (End)
%C A007091 It appears that this sequence corresponds to the numbers n for which 
               twice the sum of digits of n is the sum of digits of 2*n. [From Remy 
               Sigrist (remysigrist(AT)free.fr), Nov 22 2009]
%D A007091 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%F A007091 a(0)=0 a(n)=10*a(n/5) if n==0 (mod 5) a(n)=a(n-1)+1 otherwise. - Benoit 
               Cloitre, Dec 22, 2002
%t A007091 Table[ FromDigits[ IntegerDigits[n, 5]], {n, 0, 60}]
%o A007091 (PARI) a(n)=if(n<1,0,if(n%5,a(n-1)+1,10*a(n/5)))
%Y A007091 Cf. A000042, A007088, A007089, A007090, A007092, A007093, A007094 & A007095.
%Y A007091 Sequence in context: A098892 A037325 A037469 this_sequence A058185 A080897 
               A117383
%Y A007091 Adjacent sequences: A007088 A007089 A007090 this_sequence A007092 A007093 
               A007094
%K A007091 nonn,base,new
%O A007091 0,3
%A A007091 N. J. A. Sloane (njas(AT)research.att.com), Robert G. Wilson v (rgwv(AT)rgwv.com)

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