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 A309572 #23 Aug 11 2019 01:45:26 %S A309572 0,1,3,5,5,7,19,7,9,6,25,11,22,16,18,12,54,12,48,18,33,13,103,16,27, %T A309572 20,50,13,161,14,66,27,47,19,109,18,67,22,70,15,226,22,82,33,67,24, %U A309572 261,26,137,29,89,23,273,29,102,31,82,24,546,26,119,37,110,29 %N A309572 Number of primes of which all substrings in base n are primes. %H A309572 Rémy Sigrist, <a href="/A309572/b309572.txt">Table of n, a(n) for n = 2..2500</a> (first 199 terms from Lucas H. Gabrielli) %H A309572 Rémy Sigrist, <a href="/A309572/a309572.png">Colored logarithmic scatterplot of the first 2500 terms</a> %H A309572 Rémy Sigrist, <a href="/A309572/a309572.gp.txt">PARI program for A309572</a> %e A309572 For base 10, there are 9 primes whose substrings are also primes: 2, 3, 5, 7, 23, 37, 53, 73, and 373, thus a(10) = 9. %o A309572 (PARI) See Links section. %Y A309572 Cf. A245277. %K A309572 base,nonn %O A309572 2,3 %A A309572 _Lucas H. Gabrielli_, Aug 08 2019