A078931 Numbers k that divide prime(k)+1 or prime(k)-1.

1, 2, 3, 4, 5, 6, 10, 12, 14, 70, 72, 181, 182, 440, 1053, 6458, 6459, 6460, 6461, 6466, 6471, 40087, 40089, 100362, 251712, 251732, 251737, 251742, 637236, 637320, 637334, 637336, 1617173, 4124466, 10553445, 10553455, 10553504, 10553505, 10553547, 10553569

Offset: 1

Author

Benoit Cloitre, Jan 12 2003

Keywords

• nonn

Examples

			181 is in the sequence because the 181st prime is 1087, and 1086 is divisible by 181 (although 1088 is not so divisible).
		

Links

• Amiram Eldar, Table of n, a(n) for n = 1..198 (created using the b-files at A023143 and A045924)

Crossrefs

Cf. A000720, A023143, A045924, A162567.

Programs

Mathematica

ndpQ[n_]:=Module[{p=Prime[n]},Divisible[p-1,n]||Divisible[p+1,n]]; Select[Range[100000],ndpQ]  (* Harvey P. Dale, Apr 03 2011 *)

Formula

Equals A023143 union A045924.

a(n) = A000720(A162567(n)). - Alois P. Heinz, Feb 20 2023

Extensions

Corrected and example added by Harvey P. Dale, Apr 03 2011

Extended with terms from A023143 and A045924 by Michel Marcus, Nov 30 2013