cp's OEIS Frontend

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.

A335908 Average of those twin prime pairs p, q=p+2, for which A335884(p+1) >= A335884(p-1) and A335884(q-1) >= A335884(q+1).

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%I A335908 #5 Jul 01 2020 22:29:36
%S A335908 6,18,30,42,102,138,150,198,270,282,462,522,570,618,642,810,822,858,
%T A335908 882,1050,1062,1230,1278,1290,1302,1482,1698,1722,1878,1950,1998,2082,
%U A335908 2130,2142,2238,2310,2382,2550,2658,2730,2790,2802,2970,3258,3300,3330,3390,3462,3558,3582,3822,3918,3930,4002,4050,4158,4218,4230,4242
%N A335908 Average of those twin prime pairs p, q=p+2, for which A335884(p+1) >= A335884(p-1) and A335884(q-1) >= A335884(q+1).
%C A335908 For such twin prime pairs p, q, A335884(p) = A335884(q) = 1 + A335884((p+q)/2).
%o A335908 (PARI)
%o A335908 A335884(n) = { my(f=factor(n)); sum(k=1,#f~,if(2==f[k,1],0,f[k,2]*(1+max(A335884(f[k,1]-1),A335884(f[k,1]+1))))); };
%o A335908 isA335908(n) = (isprime(n-1)&&isprime(n+1)&&(A335884(n)>=A335884(n-2))&&(A335884(n)>=A335884(n+2)));
%Y A335908 Cf. A335884.
%Y A335908 Subsequence of A014574. Cf. also A335907.
%K A335908 nonn
%O A335908 1,1
%A A335908 _Antti Karttunen_, Jul 01 2020