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 A167777 #3 Mar 30 2012 18:52:35 %S A167777 2,4,6,12,18,30,42,60,72,102,108,138,150,180,192,198,228,240,270,282, %T A167777 312,348,420,432,462,522,570,600,618,642,660,810,822,828,858,882,1020, %U A167777 1032,1050,1062,1092,1152,1230,1278,1290,1302,1320,1428,1452,1482,1488 %N A167777 Even single (or even isolated) numbers. %C A167777 Two together with average of twin prime pairs. %p A167777 Contribution from _R. J. Mathar_, Apr 14 2010: (Start) %p A167777 isA007510 := proc(n) if isprime(n) then not isprime(n+2) and not isprime(n-2) ; else false; end if; end proc: %p A167777 isA014574 := proc(n) if not isprime(n) then isprime(n+1) and isprime(n-1) ; else false; end if; end proc: %p A167777 A167777 := proc(n) if n = 1 then 2; else for a from procname(n-1)+2 by 2 do if isA007510(a) or isA014574(a) then return(a) ; end if; end do ; end if; end proc: %p A167777 seq(A167777(n),n=1..60) ; (End) %Y A167777 Cf. A014574 (average of twin prime pairs), A167706 (the single or isolated numbers). %K A167777 nonn %O A167777 1,1 %A A167777 _Juri-Stepan Gerasimov_, Nov 11 2009