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A083059
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a(n) is the number of natural numbers k such that A078496(k)=n.
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0
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1, 0, 2, 0, 0, 0, 3, 0, 2, 0, 0, 0, 3, 0, 3, 0, 0, 0, 3, 0, 0, 0, 0, 0, 3, 0, 5, 0, 0, 0, 0, 0, 3, 0, 0, 0, 5, 0, 4, 0, 0, 0, 3, 0, 0, 0, 0, 0, 4, 0, 0, 0, 0, 0, 3, 0, 6, 0, 0, 0, 0, 0, 4, 0, 0, 0, 5, 0, 4, 0, 0, 0, 0, 0, 4, 0, 0, 0, 5, 0, 0, 0, 0, 0, 4, 0
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OFFSET
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5,3
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LINKS
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FORMULA
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a(n) = #{k: k>3 integer; A078496(k)=n}.
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EXAMPLE
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a(19)=3 since there are only k=13,16,18 for which A078496(k)=19
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PROG
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(PARI)
b(n)={forprime(p=nextprime(n+1), 2*n, if(isprime(2*n-p), return(p))); 0}
a(n)={if(isprime(n), sum(i=n\2+1, n-1, b(i)==n), 0)} \\ Andrew Howroyd, Nov 06 2019
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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Serhat Sevki Dincer (sevki(AT)ug.bilkent.edu.tr), Apr 18 2003
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EXTENSIONS
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STATUS
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approved
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