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 A318273 #15 Aug 30 2018 17:16:21 %S A318273 0,1,2,3,4,5,6,7,8,9,22,123,137,139,168,179,188,233,267,299,346,389, %T A318273 899,1124,1157,1347,1355,1469,1779,1788,2236,2346,2348,2778,3335,3779, %U A318273 11126,11133,11148,11177,11222,11238,11279,11339,11369,11579,11666,11677,11679,11699 %N A318273 Numbers with digits in nondecreasing order such that additive and multiplicative digital roots coincide. %C A318273 A299690 can be used to find terms for this sequence below some bound by prepending ones to terms while staying below that bound so the additive and multiplicative root that term matches. %C A318273 For example, 27 is in A299690 and has multiplicative root 4. 27 has the additive root 9. Prepending 4 ones gives the number 111127 which has multiplicative root 4, the same as 27 has, but it also has an additive root of 4. Furthermore, the digits are in nondecreasing order hence is in this sequence. %o A318273 (PARI) is(n) = my(cn=n); d=digits(n); if(d!=vecsort(d), return(0)); while(cn>9, d=digits(cn); cn=prod(i=1, #d, d[i])); cn-1 == (n-1)%9 || n == 0 %Y A318273 Cf. A009994, A010888, A031347, A064702, A277061, A299690. %K A318273 nonn,base %O A318273 1,3 %A A318273 _David A. Corneth_, Aug 23 2018