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 A167504 #7 Nov 11 2019 09:24:56 %S A167504 1,2,3,2,4,0,5,3,4,0,3,1,7,0,2,2,6,0,3,3,2,0,5,1,3,0,3,3,3,0,9,3,3,0, %T A167504 4,3,3,0,3,4,6,0,6,2,1,0,7,1,5,0,6,2,3,0,3,3,3,0,6,1,6,0,5,4,5,0,2,4, %U A167504 5,0,6,2,7,0,3,1,8,0,5,2,6,0,5,0,6,0,2,5,6,0,5,4,1,0,5,1,4,0,4,0,6,0,3,4,3 %N A167504 Number of primes of the form 2^(n-m) 3^m - 1, 0 <= m <= n. %H A167504 M. Underwood, <a href="http://groups.yahoo.com/group/primenumbers/message/21119">2^a*3^b one away from a prime</a>. Post to primenumbers group, Nov. 19, 2009. %H A167504 Mark Underwood, Jens Kruse Andersen, <a href="/A167504/a167504.txt">2^a*3^b one away from a prime</a>, digest of 3 messages in primenumbers Yahoo group, Nov 19, 2009. %o A167504 (PARI) A167504(n)=sum(b=0,n,ispseudoprime(3^b<<(n-b)-1)) %K A167504 nonn %O A167504 1,2 %A A167504 _M. F. Hasler_, Nov 19 2009