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A349994 a(n) is the difference between the n-th prime and the next smaller odd squarefree semiprime, divided by 2. 1

%I #7 Dec 12 2021 20:26:08

%S 1,2,1,4,5,1,1,2,4,1,1,2,1,1,2,1,3,1,1,3,4,6,7,1,2,1,2,3,2,3,1,1,3,6,

%T 1,2,2,3,5,6,1,1,3,4,6,1,2,1,2,2,1,2,5,7,8,1,1,1,2,4,1,1,3,4,6,2,1,1,

%U 1,1,4,1,3,1,1,2,2,3,1,3,1,2,4,5,7,3,1,1,1

%N a(n) is the difference between the n-th prime and the next smaller odd squarefree semiprime, divided by 2.

%H Hugo Pfoertner, <a href="/A349994/b349994.txt">Table of n, a(n) for n = 7..10000</a>

%e a(7) = (17 - 15)/2 = 1,

%e a(8) = (19 - 15)/2 = 2,

%e a(9) = (23 - 21)/2 = 1,

%e a(10) = (29 - 21)/2 = 4.

%o (PARI) forprime(p=17,500,forstep(k=p-2,15,-2,if(omega(k)==2&&bigomega(k)==2, print1((p-k)/2,", ");break)))

%Y Cf. A046388.

%K nonn

%O 7,2

%A _Hugo Pfoertner_, Dec 12 2021

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