%I #4 Dec 05 2013 19:55:57
%S 1,12,1236,1234764,12345170472,1234566427881888,
%T 1234567662448315881888,123456781059643537568590582656,
%U 12345678970161821174363821245734078592,123456789109025621175870796087877366124764227584
%N a(1) = 1, a(n) for n > 1 is the smallest multiple of a(n-1) that begins with the concatenation 123... up to n.
%e For n = 3 we have a(n-1) = a(2) = 12; 103*12 = 1236 is the smallest multiple of a(2) that begins with 123, so a(3) = 1236.
%o (PARI) {print1(a=1,","); for(n=2,10,k=floor(log(a)/log(10))+1; v=Str(1); for(i=2,n, v=concat(v,Str(i))); s=eval(v); t=s+1; m=floor(log(s)/log(10))+1; d=k-m; s=s*10^d; t=t*10^d; b=1; j=d; while(b>0,q=floor(s/a); while(b>0&&(p=q*a)<t,if(p>=s,print1(p,","); b=0,q++)); s=10*s; t=10*t); a=p)}
%Y Cf. A078395, A078396, A078397.
%K base,nonn
%O 1,2
%A _Amarnath Murthy_, Nov 26 2002
%E Edited and extended by _Klaus Brockhaus_, Dec 06 2002