A147825 - OEIS

%I #13 Mar 21 2016 03:13:11

%S 0,5,14,23,122,599,833,1427,9986,11111,599999,590909,749999,3769223,

%T 13571357,53333333,187499993,294117647,1111111111,3684210521,

%U 149999999999,37619047619,590909090909,391304347826,2916666666662,23999999999999,23076923076923,37037037037037

%N Minimum number k for which the digital sum of k*n is 5*n.

%H Chai Wah Wu, <a href="/A147825/b147825.txt">Table of n, a(n) for n = 0..39</a>

%p P:=proc(i) local j,k,n,ok,w; for n from 0 by 1 to i do j:=-1; ok:=1; while ok=1 do j:=j+1; w:=0; k:=n*j; while k>0 do w:=w+k-(trunc(k/10)*10); k:=trunc(k/10); od; if w=5*n then ok:=0; print(j); fi; od; od; end: P(100);

%o (PARI) a(n) = {my(k = 0); while (sumdigits(k*n) != 5*n, k++); k;}; \\ _Michel Marcus_, Mar 21 2016

%Y Cf. A147822-A147824, A147826-A147831.

%K easy,nonn,base

%O 0,2

%A _Paolo P. Lava_ and _Giorgio Balzarotti_, Nov 14 2008

%E Edited by _Charles R Greathouse IV_, Nov 01 2009

%E a(11)-a(21) from _Donovan Johnson_, Sep 16 2012

%E a(22)-a(27) from _Chai Wah Wu_, Mar 20 2016