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 A013605 #15 Aug 14 2019 08:35:27 %S A013605 2,2,12,6,4,6,4,44,16,6,12,12,52,2,4,62,16,102,16,26,54,54,36,38,64,2, %T A013605 12,42,16,102,18,72,42,68,256,18,52,84,234,54,34,72,274,266,36,14,4, %U A013605 56,162,2,24,122,6,14,94,446,72,56,298,384,28,26 %N A013605 a(n) = 5^n-prevprime(5^n). %H A013605 Daniel Starodubtsev, <a href="/A013605/b013605.txt">Table of n, a(n) for n = 1..1000</a> %p A013605 seq(5^i-prevprime(5^i),i=1..100); %t A013605 #-NextPrime[#,-1]&/@(5^Range[70]) (* _Harvey P. Dale_, Mar 12 2011 *) %o A013605 (PARI) a(n) = 5^n - precprime(5^n-1); \\ _Michel Marcus_, Aug 14 2019 %Y A013605 Cf. A000351, A104090. %K A013605 nonn %O A013605 1,1 %A A013605 James Kilfiger (mapdn(AT)csv.warwick.ac.uk)