A125167 Numbers n such that the n-th prime + n-th nonprime is itself prime.

1, 2, 3, 6, 7, 15, 20, 26, 29, 30, 35, 40, 42, 43, 46, 52, 57, 61, 65, 70, 75, 84, 92, 99, 100, 102, 105, 125, 139, 140, 144, 149, 154, 164, 171, 179, 183, 197, 202, 214, 218, 223, 227, 232, 234, 245, 247, 251, 258, 265, 272, 280, 288, 290, 294, 299, 304, 323, 325

Offset: 1

Author

Jason G. Wurtzel, Nov 22 2006

Keywords

• easy
• nonn

Examples

			The 15th prime is 47, while the 15th nonprime is 24. 47+24=71 which is itself prime. Similarly, the 30th prime is 113, while the 30th nonprime is 44. 113+44=157 which is prime.
		

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A000040, A018252, A022797.

Programs

Mathematica

Module[{nn=500,np,tbl},np=Select[Range[nn],!PrimeQ[#]&];tbl=Table[{n,np[[n]]+Prime[n]},{n,Length[ np]}];Select[tbl,PrimeQ[#[[2]]]&]][[;;,1]] (* Harvey P. Dale, Sep 21 2023 *)

Extensions

More terms from Klaus Brockhaus, Nov 23 2006