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%I #13 Nov 28 2017 15:53:38
%S 0,0,1,2,3,2,3,3,3,3,5,3,5,4,3,4,3,6,4,5,4,4,5,4,6,4,4,5,4,4,7,4,5,7,
%T 5,6,5,5,7,4,5,6,4,5,5,5,5,6,8,4,7,4,5,6,5,4,3,8,8,5,5,5,7,7,5,5,9,4,
%U 7,8,8,6,7,4,5,7,4,7,7,6,8,7,5,5,6,7,6
%N a(n) is the number of natural numbers k such that A078496(k) = prime(n), where prime(n) denotes the n-th prime.
%H Iain Fox, <a href="/A083060/b083060.txt">Table of n, a(n) for n = 1..10000</a>
%F For n > 2, a(n) = card({k: k > 3; A078496(k) = prime(n)}).
%e a(3)=1 since there is only k=4 for A078496(k) = prime(3) = 5.
%e a(8)=3 since there is only k=13,16,18 for A078496(k) = prime(8) = 19.
%o (PARI) A078496(n) = {my(p=nextprime(n+1)); while(!isprime(2*n-p), p = nextprime(p+1)); p; }
%o first(n) = { my(res=vector(n)); for(x=4, prime(n), my(r=primepi(A078496(x))); if(r <= n, res[r]++)); res; } \\ _Iain Fox_, Nov 23 2017
%Y Cf. A078496.
%K easy,nonn
%O 1,4
%A Serhat Sevki Dincer (sevki(AT)ug.bilkent.edu.tr), Apr 18 2003
%E a(1) and a(2) prepended by _Iain Fox_, Nov 23 2017
%E More terms from _Iain Fox_, Nov 23 2017