This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A078931 #27 Sep 06 2024 14:08:16
%S A078931 1,2,3,4,5,6,10,12,14,70,72,181,182,440,1053,6458,6459,6460,6461,6466,
%T A078931 6471,40087,40089,100362,251712,251732,251737,251742,637236,637320,
%U A078931 637334,637336,1617173,4124466,10553445,10553455,10553504,10553505,10553547,10553569
%N A078931 Numbers k that divide prime(k)+1 or prime(k)-1.
%H A078931 Amiram Eldar, <a href="/A078931/b078931.txt">Table of n, a(n) for n = 1..198</a> (created using the b-files at A023143 and A045924)
%F A078931 Equals A023143 union A045924.
%F A078931 a(n) = A000720(A162567(n)). - _Alois P. Heinz_, Feb 20 2023
%e A078931 181 is in the sequence because the 181st prime is 1087, and 1086 is divisible by 181 (although 1088 is not so divisible).
%t A078931 ndpQ[n_]:=Module[{p=Prime[n]},Divisible[p-1,n]||Divisible[p+1,n]]; Select[Range[100000],ndpQ] (* _Harvey P. Dale_, Apr 03 2011 *)
%Y A078931 Cf. A000720, A023143, A045924, A162567.
%K A078931 nonn
%O A078931 1,2
%A A078931 _Benoit Cloitre_, Jan 12 2003
%E A078931 Corrected and example added by _Harvey P. Dale_, Apr 03 2011
%E A078931 Extended with terms from A023143 and A045924 by _Michel Marcus_, Nov 30 2013