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 A274943 #5 Jul 09 2025 04:41:21 %S A274943 -1,-1,100,1425,-1,389305,8946176,225331713,6210001000,186492227801, %T A274943 6073061476032,213404945384449,8054585122464440,325144322753909625, %U A274943 13983676842985394176 %N A274943 Smallest self-descriptive number in base b, or -1 if no such number exists. %C A274943 A self-descriptive number in base b has b digits, indexed by 0 ... b-1 and for all n, the n-th digit equals the number of n's in the number. In base 10 there is exactly one such number, 6210001000. %e A274943 1210_4 = 100, 21200_5 = 1425, 3211000_7 = 389305, %e A274943 42101000_8 = 8946176, 521001000_9 = 225331713, 6210001000_10, %e A274943 72100001000_11 = 186492227801, 821000001000_12 = 6073061476032, %e A274943 9210000001000_13 = 213404945384449, (10)2100000001000_14 = %e A274943 8054585122464440, (11)21000000001000_15 = 325144322753909625, %e A274943 (12)21000000001000_16 = 13983676842985394176, etc. %Y A274943 Very similar to A108551. %K A274943 sign,base,more %O A274943 2,3 %A A274943 _N. J. A. Sloane_, Jul 23 2016, following an email from Amarnath Krishnamurthy [_Amarnath Murthy_] and in addition using data from A108551