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 A306106 #8 Oct 06 2018 09:37:51
%S A306106 0,1,2,3,10,20,21,30,31,32,101,102,103,201,202,203,212,213,301,302,
%T A306106 303,312,313,323,1010,1020,1021,1030,1031,1032,2010,2020,2021,2030,
%U A306106 2031,2032,2120,2121,2130,2131,2132,3010,3020,3021,3030,3031,3032,3120,3121,3130,3131,3132,3230,3231,3232,10101,10102,10103
%N A306106 Numbers with digits in {0,1,2,3} such that every other digit is strictly less than its neighbors.
%C A306106 Terms of A032859 written in base 4.
%F A306106 a(n) = A007090(A032859(n)).
%F A306106 Terms in A297147 having only digits < 4; intersection of A297147 and A007090.
%o A306106 (PARI) A(Nmax=100, K=3, A=[0..K], i=vector(2*K, i, max(1, i-K+1)), c(T, v)=apply(t->t+T, v))={for(n=0, oo, for(k=10, K*11, if(k%10<k\10, k%10|| i=concat(i, 1+#A); A=concat(A, c(k*10^n, A[i[K*n+k%10+1]..i[K*n+K+1]-1])); #A<Nmax||return(A))))}
%Y A306106 Cf. A306105 .. A306111 and A297147: analog for bases 3..9 and 10.
%Y A306106 Cf. A032859 and A032858 .. A032865 for other bases 3..10.
%K A306106 nonn,base
%O A306106 1,3
%A A306106 _M. F. Hasler_, Oct 05 2018