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 A018143 #14 Jul 08 2025 06:28:45 %S A018143 1,2,3,4,7,10,16,26,40,64,100,159,252,399,631,1000,1585,2512,3982, %T A018143 6310,10000,15849,25119,39811,63096,100000,158490,251189,398108, %U A018143 630958,1000000,1584894,2511887,3981072,6309574 %N A018143 Powers of fifth root of 10 rounded up. %t A018143 Ceiling[Surd[10,5]^Range[0,40]] (* _Harvey P. Dale_, Dec 30 2017 *) %o A018143 (PARI) a(n) = sqrtnint(10^n-1, 5) + 1; \\ _Michel Marcus_, Jun 26 2024 %Y A018143 Cf. A018141, A018142. %K A018143 nonn %O A018143 0,2 %A A018143 _N. J. A. Sloane_