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A335907 Average of those twin prime pairs p, q=p+2, for which A335885(p+1) <= A335885(p-1) and A335885(q-1) <= A335885(q+1). 2

%I #10 Jul 01 2020 22:29:27

%S 4,12,72,102,108,180,192,240,348,420,600,822,828,1032,1050,1152,1302,

%T 1320,1428,1488,1608,1722,1872,2088,2112,2550,2592,2688,2712,3000,

%U 3168,3252,3360,3372,3468,3528,3672,3768,4020,4092,4128,4272,4650,4800,4932,5100,5232,5280,5520,5640,5868,5880,6132,6690,6762,6780

%N Average of those twin prime pairs p, q=p+2, for which A335885(p+1) <= A335885(p-1) and A335885(q-1) <= A335885(q+1).

%C For such twin prime pairs p, q, A335885(p) = A335885(q) = 1 + A335885((p+q)/2).

%o (PARI)

%o A335885(n) = { my(f=factor(n)); sum(k=1,#f~,if(2==f[k,1],0,f[k,2]*(1+min(A335885(f[k,1]-1),A335885(f[k,1]+1))))); };

%o isA335907(n) = (isprime(n-1)&&isprime(n+1)&&(A335885(n)<=A335885(n-2))&&(A335885(n)<=A335885(n+2)));

%Y Cf. A335885.

%Y Subsequence of A014574. Cf. also A335908.

%K nonn

%O 1,1

%A _Antti Karttunen_, Jul 01 2020

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Last modified March 28 20:05 EDT 2024. Contains 371254 sequences. (Running on oeis4.)