This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A113558 #10 Mar 27 2018 08:44:33
%S A113558 3,130,123,10032,100030,1000032,1000013,100000032,100000053,
%T A113558 10000000030,10000000043,1000000000032,1000000000103,100000000000138,
%U A113558 1000000000000035,10000000000000032,10000000000000033,1000000000000000134
%N A113558 Least multiple of n in which the n-th digit from left is 3.
%e A113558 a(4)= 10032, in which the fourth digit is 3.
%o A113558 (PARI) dig(n,digno,base) = { local(nshif) ; nshif=n ; for(shifr=0,digno-1, nshif = floor(nshif/base) ; ) ; nshif % base ; } ndig(n,base) = { local(nshif,resul) ; nshif=n ; resul=1 ; while(nshif>0, nshif = floor(nshif/base) ; if( nshif>0, resul++, break) ; ) ; return(resul) ; } { for (n = 1, 23, anmin=10^(n-1) ; if ( ( n % 2 == 0 ) || (n %5 == 0), anmin *= 10) ; if ( ( n % 20 == 0 ) || (n %50 == 0), anmin *= 10) ; for( nex = anmin,anmin+10000000000000000000000, if ( ( nex % n) != 0, next ; ) ; nexd=ndig(nex,10) ; if( dig(nex,nexd-n,10)==3, print(nex,",") ; break ; ) ; ); ) } \\ _R. J. Mathar_, Mar 15 2006
%Y A113558 Cf. A113556, A113557.
%K A113558 base,easy,nonn
%O A113558 1,1
%A A113558 _Amarnath Murthy_, Nov 06 2005
%E A113558 More terms from _R. J. Mathar_, Mar 15 2006