OFFSET
1,6
COMMENTS
Conjecture: a(3n+9) > a(3n+8) and a(3n+10) < a(3n+9) for n>=1. - Anthony Browne, Jun 26 2016
LINKS
J. Stauduhar, Table of n, a(n) for n = 1..10000
FORMULA
EXAMPLE
For n=6, 2*6=12 and the partitions of 12 are (1,11),(2,10),(3,9),(4,8),(5,7),(6,6). Of these, 2 are composite pairs, namely (4,8),(6,6) so a(6)=2.
MATHEMATICA
Table[Count[Transpose@ {#, 2 n - #} &@ Range@ n, w_ /; Times @@ Boole@ Map[CompositeQ, w] > 0], {n, 69}] (* Michael De Vlieger, Jun 26 2016 *)
PROG
(PARI) a(n) = sum(k=1, n-1, (1-isprime(k+1))*(1-isprime(2*n-k-1))); \\ Michel Marcus, Apr 11 2022
CROSSREFS
KEYWORD
nonn
AUTHOR
J. Stauduhar, Apr 16 2013
STATUS
approved