cp's OEIS Frontend

A131382 Minimal number m such that Sum_digits(n*m)=n.

%I A131382 #34 Feb 19 2022 11:19:24
%S A131382 1,1,1,1,1,1,1,1,1,19,19,4,19,19,13,28,28,11,46,199,19,109,73,37,199,
%T A131382 73,37,271,172,1333,289,559,1303,847,1657,833,1027,1576,1282,17497,
%U A131382 4339,2119,2323,10909,11111,12826,14617,14581,16102,199999,17449,38269
%N A131382 Minimal number m such that Sum_digits(n*m)=n.
%H A131382 Peter Lomax, <a href="/A131382/b131382.txt">Table of n, a(n) for n = 1..1000</a> (first 90 terms from T. D. Noe)
%H A131382 H. Fredricksen, E. J. Ionascu, F. Luca, and P. Stanica, <a href="http://arxiv.org/abs/0803.0477">Minimal Niven numbers</a>, arXiv:0803.0477 [math.NT], 2008.
%H A131382 Peter Lomax, <a href="/A131382/a131382_2.txt">Phix program for generating 1000 terms</a>
%F A131382 a(n) = A002998(n) / n. - _Michel Marcus_, Dec 10 2012
%e A131382 n=23 --> a=73 because 23*73 = 1679 and 1+6+7+9=23.
%e A131382 n=34 --> a=847 because 34*847 = 28798 and 2+8+7+9+8=34.
%p A131382 P:=proc(n) local i,j,k,w; for i from 1 by 1 to n do for j from 1 to n do w:=0; k:=i*j; while k>0 do w:=w+k-(trunc(k/10)*10); k:=trunc(k/10); od; if i=w then print(j); break; fi; od; od; end: P(1000000);
%t A131382 m[n_]:=Module[{m=1},While[Total[IntegerDigits[m*n]]!=n,m++];m]; Array[m,60] (* _Harvey P. Dale_, Sep 28 2013 *)
%o A131382 (PARI) a(n)=my(k);while(sumdigits(k+=n)!=n,); k/n \\ _Charles R Greathouse IV_, Feb 01 2013
%Y A131382 Cf. A005349, A002998.
%K A131382 base,nonn
%O A131382 1,10
%A A131382 _Paolo P. Lava_ and _Giorgio Balzarotti_, Jul 09 2007