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 A167505 #7 Nov 11 2019 09:25:02 %S A167505 1,2,2,2,3,2,3,4,4,3,2,0,5,1,1,6,6,2,5,1,1,2,5,0,3,1,2,2,4,2,5,3,0,1, %T A167505 6,2,8,2,2,3,9,1,7,4,4,0,6,0,3,3,2,7,8,1,4,4,1,2,6,0,5,2,4,2,2,1,11,4, %U A167505 3,1,3,0,6,0,2,3,4,1,6,0,4,3,8,2,2,2,2,1,3,1,2,3,3,1,3,0,5,1,2,1,7,0,7,2,2 %N A167505 Number of primes of the form 2^(n-m) 3^m + 1, 0 <= m <= n. %H A167505 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 A167505 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 A167505 (PARI) A167505(n)=sum(b=0,n,ispseudoprime(3^b<<(n-b)+1)) %Y A167505 Cf. A167504, A167506. %K A167505 nonn %O A167505 1,2 %A A167505 _M. F. Hasler_, Nov 19 2009