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

1,2

Links

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

Example

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.

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 *)

Crossrefs

Cf. A000040, A018252, A022797.

Sequence in context: A294524 A032882 A265394 * A137604 A034901 A343149

Adjacent sequences: A125164 A125165 A125166 * A125168 A125169 A125170

Keyword

easy,nonn

Author

Jason G. Wurtzel, Nov 22 2006

Extensions

More terms from Klaus Brockhaus, Nov 23 2006

Status

approved