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 A193413 #26 Aug 03 2022 02:35:00 %S A193413 1,2,3,4,5,6,7,8,9,11,22,33,44,55,66,77,88,99,101,111,202,212,222,303, %T A193413 313,323,333,404,414,424,434,444,505,515,525,535,545,555,606,616,626, %U A193413 636,646,656,666,707,717,727,737,747,757,767,777,808,818,828,838,848,858,868,878,888,909,919,929,939,949,959,969,979,989,999,1001 %N A193413 Valley numbers. %C A193413 For n > 10 the structure of digits represents a valley. The first digit is equal to the last digit (1 - 9). The first digits are in nonincreasing order. The last digits are in nondecreasing order. The numbers may have more than one smallest digit. Sequence is infinite. %C A193413 Superset of crater numbers (A193409) and A193412. %C A193413 See valley numbers in base 2 (A193414 and A193415). %e A193413 Illustration using 6543333346: %e A193413 6 . . . . . . . . 6 %e A193413 . 5 . . . . . . . . %e A193413 . . 4 . . . . . 4 . %e A193413 . . . 3 3 3 3 3 . . %Y A193413 Cf. A110785, A193409, A193412, A193414, A193415. %Y A193413 Cf. A134970. - _Omar E. Pol_, Aug 05 2011 %K A193413 nonn,base %O A193413 1,2 %A A193413 _Jaroslav Krizek_, Jul 25 2011 %E A193413 More terms extended by definition by _Jaroslav Krizek_, Jul 27 2011