OFFSET
1,2
COMMENTS
a(1)=1, for n>1: if (prime(n)-1)/2 is odd/even then a(n) is the next prime/composite number.
MATHEMATICA
p=Prime[Range[100]]; s=Complement[Range[100], p]; bb={1}; is=1; ip=0; Do[If[EvenQ[(Prime[i]-1)/2], is=is+1; bb=Append[bb, s[[is]]], ip=ip+1; bb=Append[bb, p[[ip]]]], {i, 2, 60}]; bb
CROSSREFS
KEYWORD
nonn
AUTHOR
Zak Seidov, Apr 01 2005
STATUS
approved