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 A215641 #30 May 06 2022 13:13:51 %S A215641 2,211,211151,2111011129,211101100910009,211101100910007100049, %T A215641 2111011009100071000031000453,211101100910007100003100000310000721, %U A215641 211101100910007100003100000310000019100000543,2111011009100071000031000003100000191000000071000000531 %N A215641 Smallest prime whose decimal expansion consists of the concatenation of a 1-digit prime, a 2-digit prime, a 3-digit prime, ..., and an n-digit prime. %C A215641 It is a plausible conjecture that a(n) always exists. %C A215641 a(n) has A000217(n) = n*(n+1)/2 digits. %e A215641 a(4) = 2111011129, the smallest prime formed from a single-digit, a double-digit, a triple-digit, and a quadruple-digit prime, i.e., 2, 11, 101, 1129. %Y A215641 Cf. A000040, A000217, A003617. %Y A215641 Subsequence of A195302. %Y A215641 Cf. A338968 (similar, with largest prime). %K A215641 nonn,base %O A215641 1,1 %A A215641 _Jonathan Vos Post_, Aug 18 2012 %E A215641 Edited by _N. J. A. Sloane_, Aug 18 2012