cp's OEIS Frontend

A105287 Numbers k such that prime(k+1) == 2 (mod k).

%I A105287 #32 Aug 31 2024 21:44:44
%S A105287 1,9,67,437,441,2615,100349,100353,100359,637197,637305,27066969,
%T A105287 27067049,27067101,27067113,27067115,179992839,179993001,55762149071,
%U A105287 382465573491
%N A105287 Numbers k such that prime(k+1) == 2 (mod k).
%C A105287 Integers k such that A004649(k+1) = 2. - _Michel Marcus_, Dec 30 2022
%t A105287 bb={};Do[If[2==Mod[Prime[n+1], n], bb=Append[bb, n]], {n, 1, 200000}];bb
%t A105287 With[{nn=640000},Flatten[Position[Thread[{Range[nn],Prime[Range[2,nn+1]]}], _?(Mod[Last[#]-2,First[#]]==0&),{1},Heads->False]]] (* _Harvey P. Dale_, Sep 23 2021 *)
%o A105287 (Sage)
%o A105287 def A105287(max) :
%o A105287     terms = []
%o A105287     p = 3
%o A105287     for n in range(1, max+1) :
%o A105287         if (p - 2) % n == 0 : terms.append(n)
%o A105287         p = next_prime(p)
%o A105287     return terms
%o A105287 # _Eric M. Schmidt_, Feb 05 2013
%Y A105287 Cf. A004649, A105286, A105288, A105290, A105329, A105451.
%K A105287 nonn,more
%O A105287 1,2
%A A105287 _Zak Seidov_, Apr 25 2005
%E A105287 First term inserted by _Eric M. Schmidt_, Feb 05 2013
%E A105287 More terms from _Harvey P. Dale_, May 04 2013
%E A105287 a(12)-a(18) from _Michel Marcus_, Dec 29 2022
%E A105287 a(19)-a(20) from _Max Alekseyev_, Aug 31 2024