A295430 - OEIS

%I #16 Feb 20 2018 22:51:21

%S 3,30,30,32,30,30,35,32,36,30,33,36,39,308,30,32,34,36,38,300,315,308,

%T 322,312,300,312,324,308,319,300,310,320,330,306,315,324,333,304,312,

%U 320,328,336,301,308,315,322,329,336,343,300,306,312,318,324,330,336,342,348,354,300,305,310,315

%N a(n) is the least nontrivial multiple of n that begins with 3.

%H Robert Israel, <a href="/A295430/b295430.txt">Table of n, a(n) for n = 1..10000</a>

%p f:= proc(n) local m,k;

%p   for m from 0 do

%p     k := max(2, ceil(3*10^m/n));

%p     if k*n < 4*10^m then return k*n end if

%p   end do

%p end proc:

%p seq(f(i),i=1..100);

%o (PARI) a(n) = {my(k=2); while(digits(k*n)[1] != 3, k++); k*n;} \\ _Michel Marcus_, Feb 13 2018

%o (Python)

%o def A295430(n):

%o     m = 2*n

%o     while True:

%o         if str(m)[0] == '3':

%o             return m

%o         m += n # _Chai Wah Wu_, Feb 13 2018

%Y Cf. A082792.

%K nonn

%O 1,1

%A _Robert Israel_, Feb 12 2018