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 A067670 #17 Feb 16 2025 08:32:45 %S A067670 2,11,19,199,29998999999999999999999 %N A067670 Smallest prime of additive persistence n. %C A067670 a(5) >= 29*10^2222222222222222222221-1, the next number of additive persistence 5 after A006050(5). (a(5) is not equal to A006050(5) because that number is divisible by 313.) - _Pontus von Brömssen_, Oct 17 2023 %D A067670 H. J. Hindin, The additive persistence of a number, J. Rec. Math., 7 (No. 2, 1974), 134-135. %H A067670 N. J. A. Sloane, <a href="http://neilsloane.com/doc/persistence.html">The persistence of a number</a>, J. Recreational Math., 6 (1973), 97-98. %H A067670 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/AdditivePersistence.html">Additive Persistence</a> %F A067670 a(n) >= A006050(n). - _Pontus von Brömssen_, Oct 17 2023 %e A067670 a(2) = 19, 19 -> 10 -> 1, so 2 summation steps are required to reach a single-digit number. %Y A067670 Cf. A003001, A045646, A006050. %K A067670 hard,nonn,base %O A067670 0,1 %A A067670 _Shyam Sunder Gupta_, Feb 23 2002