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 A270173 #11 Mar 16 2016 16:48:22 %S A270173 0,90,80,70,60,50,40,30,20,10,100,190,180,170,160,150,140,130,120, %T A270173 1010,1200,1290,1280,1270,1260,1250,1240,1230,10120,12010,12300,12390, %U A270173 12380,12370,12360,12350,12340,101230,120120,123010,123400,123490,123480,123470 %N A270173 Smallest number k such that A270172(k) = n. %o A270173 (PARI) eva(n) = subst(Pol(n), x, 10) %o A270173 increasedigits(n) = my(d=digits(n)); for(k=1, #d, d[k]++; if(d[k]==10, d[k]=0)); eva(d) %o A270173 a270172(n) = my(x=n, i=0); while(#Str(x) > 1, x=increasedigits(x); i++); i %o A270173 a(n) = my(k=0); while(a270172(k)!=n, k++); k %Y A270173 Cf. A269667, A270172. %K A270173 nonn,base %O A270173 0,2 %A A270173 _Felix Fröhlich_, Mar 12 2016