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A034052 Numbers with multiplicative digital root value 5.

%I A034052 #50 Feb 16 2025 08:32:37
%S A034052 5,15,35,51,53,57,75,115,135,151,153,157,175,315,351,355,359,395,511,
%T A034052 513,517,531,535,539,553,557,571,575,579,593,597,715,751,755,759,795,
%U A034052 935,953,957,975,1115,1135,1151,1153,1157,1175,1315,1351,1355,1359,1395
%N A034052 Numbers with multiplicative digital root value 5.
%C A034052 All digits of a(n) must be odd. - _Robert Israel_, Oct 19 2015
%H A034052 Robert Israel, <a href="/A034052/b034052.txt">Table of n, a(n) for n = 1..10000</a>
%H A034052 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/MultiplicativeDigitalRoot.html">Multiplicative Digital Root</a>
%H A034052 <a href="/index/Ar#10-automatic">Index entries for 10-automatic sequences</a>.
%p A034052 mdr:= proc(n) option remember;
%p A034052 if n < 10 then return(n) fi;
%p A034052 procname(convert(convert(n,base,10),`*`))
%p A034052 end proc:
%p A034052 select(mdr=5, [$1..10^5]); # _Robert Israel_, Oct 19 2015
%t A034052 mrQ[n_]:=NestWhile[Times@@IntegerDigits[#]&,n,#>10&]==5; Select[Range[1395],mrQ[#]&] (* _Jayanta Basu_, May 30 2013 *)
%o A034052 (PARI) t(n) = {while(n>9, n=prod(i=1, #n=digits(n), n[i])); n};
%o A034052 for(n=0, 1e4, if(t(n) == 5, print1(n", "))); \\ _Altug Alkan_, Oct 19 2015
%Y A034052 Cf. A031347, A371561.
%Y A034052 Cf. A034048, A002275, A034049, A034050, A034051, this sequence, A034053, A034054, A034055, A034056 (numbers having multiplicative digital roots 0-9).
%K A034052 nonn,base,easy
%O A034052 1,1
%A A034052 _Patrick De Geest_, Sep 15 1998
%E A034052 Incorrect formula removed by _Martin Renner_, Oct 19 2015