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 A006307 M0344 #29 Dec 26 2021 21:32:37 %S A006307 0,0,1,1,2,2,5,3,8,11,22,25,53,76,151,244,435,749,1314,2367,4239,7471, %T A006307 13705,24928,45746,83467,153850,283746,525236,975685,1817111,3390038, %U A006307 6341424,11891654,22336060,42034097,79287664,149711134,283277225,536710100,1018369893 %N A006307 Number of ways writing 2^n as unordered sums of 2 primes. %D A006307 Bohman, Jan and Froberg, Carl-Erik; Numerical results on the Goldbach conjecture. Nordisk Tidskr. Informationsbehandling (BIT) 15 (1975), no. 3, 239-243. %D A006307 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). %H A006307 <a href="/index/Go#Goldbach">Index entries for sequences related to Goldbach conjecture</a> %F A006307 a(n) = A061358(2^n). %e A006307 n = 5: 2^5 = 32 = 3+29 = 13+19 so a(5) = 2. %p A006307 a:=proc(n) local c,k; c:=0: for k from 1 to floor((n-1)/2) do if isprime(2*k+1)=true and isprime(2*n-2*k-1)=true then c:=c+1 else c:=c fi od end: 0,0,1,seq(a(2*2^n),n=1..15); # _Emeric Deutsch_, Sep 22 2004 %o A006307 (PARI) a(n)=my(N=2^n,s); forprime(q=2, N\2, s+=isprime(N-q)); s \\ _Charles R Greathouse IV_, Mar 02 2015 %Y A006307 Cf. A061358, A062602, A062610. %K A006307 nonn %O A006307 0,5 %A A006307 _N. J. A. Sloane_ %E A006307 More terms from _David W. Wilson_ %E A006307 a(28)-a(35) from _Ray Chandler_, Feb 21 2004 %E A006307 a(36)=79287664 and a(37)=149711134 from _Ray Chandler_, Apr 10 2005 %E A006307 a(38)-a(40) from _Russ Cox_, Nov 04 2006