OFFSET
1,6
COMMENTS
Conjecture: all items for n>=4 are greater than or equal to 1. This is a stronger conjecture than the Goldbach conjecture.
LINKS
R. J. Mathar, Table of n, a(n) for n = 1..10777
EXAMPLE
For 2*4+1 = 9 we have just one such composition: 9 = 2*3+3, so a(4)=1;
For 2*14+1 = 29 we have four such compositions: 29 = 2*3+23 = 2*5+19 = 2*11+7 = 2*13+3, so a(14)=4.
MAPLE
A103151 := proc(n)
local s, a, q;
a := 0 ;
s := 2*n+1 ;
for pi from 2 do
q := s-2*ithprime(pi) ;
if q <=2 then
return a ;
else
if isprime(q) then
a := a+1 ;
end if;
end if;
end do:
end proc: # R. J. Mathar, Feb 22 2014
MATHEMATICA
Do[m = 3; ct = 0; While[(m*2) < n, If[PrimeQ[m], cp = n - (2*m); If[ PrimeQ[cp], ct = ct + 1]]; m = m + 2]; Print[ct], {n, 9, 299, 2}]
PROG
CROSSREFS
KEYWORD
nonn
AUTHOR
Lei Zhou, Feb 09 2005
EXTENSIONS
Edited and Scheme-code added by Antti Karttunen, Jun 19 2007
STATUS
approved