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A083059 a(n) is the number of natural numbers k such that A078496(k)=n. 0
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

5,3

LINKS

Table of n, a(n) for n=5..90.

FORMULA

a(n) = #{k: k>3 integer; A078496(k)=n}.

EXAMPLE

a(19)=3 since there are only k=13,16,18 for which A078496(k)=19

PROG

(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

CROSSREFS

Cf. A078496.

Sequence in context: A322977 A321374 A262889 * A173440 A330936 A284687

Adjacent sequences:  A083056 A083057 A083058 * A083060 A083061 A083062

KEYWORD

easy,nonn

AUTHOR

Serhat Sevki Dincer (sevki(AT)ug.bilkent.edu.tr), Apr 18 2003

EXTENSIONS

Terms a(24) and beyond from Andrew Howroyd, Nov 06 2019

STATUS

approved

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Last modified January 20 19:53 EST 2020. Contains 331096 sequences. (Running on oeis4.)