A103273 Number of ways of writing prime(n)-1 in the form prime(i)+prime(j).

0, 0, 1, 1, 2, 1, 2, 2, 3, 2, 3, 4, 3, 4, 4, 3, 4, 6, 6, 5, 6, 7, 5, 4, 7, 6, 8, 6, 8, 7, 10, 7, 5, 8, 5, 12, 11, 10, 6, 6, 7, 14, 8, 11, 9, 13, 19, 11, 7, 12, 7, 9, 18, 9, 8, 9, 9, 19, 16, 14, 16, 8, 15, 12, 17, 10, 24, 19, 9, 16, 10, 10, 18, 18, 22, 10, 9, 21, 14, 20, 11, 30, 14, 19, 21, 13, 13

Offset: 1

Author

Yasutoshi Kohmoto, Jan 27 2005

Keywords

• nonn

Examples

			11-1=3+7=5+5, so a(5)=2.
		

Programs

Mathematica

Table[Count[IntegerPartitions[p-1,{2}],?(AllTrue[#,PrimeQ]&)],{p,Prime[ Range[90]]}] (* The program uses the AllTrue function from Mathematica version 10 *) (* _Harvey P. Dale, Sep 09 2019 *)

Formula

a(n) = A061358(prime(n)-1). - David Wasserman, Oct 08 2005

Extensions

More terms from David Wasserman, Oct 08 2005