Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #5 Dec 05 2013 19:55:47
%S 1,10,210,5432,43210,543210,2111019876,98765432,876543210,9876543210,
%T 918171615141312111019,3121110198765432,716151413121110198765,
%U 7161514131211101987654,41312111019876543210
%N Smallest multiple of n which is a reverse concatenation of n nonnegative consecutive numbers, or 0 if no such multiple exists.
%C a(20k)=a(50k)=0 for any k. On the other hand, a(n) is nonzero if n is not multiple of 10. - _Max Alekseyev_, Feb 15 2005
%o (PARI) {len10(m) = ceil(log(m+1)/log(10))} {reverse(n) = m=0;while(n,m=m*10+(n%10);n\=10);return(m)} {a(n) = local(m); for(s=0,10^6,m=0;for(i=0,n-1,m=m*10^len10(s+i)+s+i);m=reverse(m);if(s==0,m*=10);if(m%n==0,return(m));if(n%10==0,return(0)))} (Alekseyev)
%Y Cf. A077691.
%K base,nonn
%O 1,2
%A _Amarnath Murthy_, Nov 16 2002
%E More terms from _Max Alekseyev_, Feb 15 2005