login
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
OFFSET
5,3
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 A348341 A330936
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