OFFSET
0,3
COMMENTS
FORMULA
a(n) = convolve(p,c) + convolve(c,p) = 2*convolve(p,c) where p(n) = 1 if 2n+1 is prime and 0 otherwise, and c(n) = 1 if 2n+1 is nonprime and 0 otherwise.
EXAMPLE
n=15, 2*n=30, 2*n = { 3+27, 5+25, 29+1; 1+29, 25+5, 27+3 }, a(15) = 6
n=18, 2*n=36, 2*n = { 3+33, 11+25; 11+25, 33+3 }, a(18) = 4
CROSSREFS
KEYWORD
nonn
AUTHOR
Peter A. Lawrence, Aug 11 2012
STATUS
approved