A105287 - OEIS

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A105287

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

1, 9, 67, 437, 441, 2615, 100349, 100353, 100359, 637197, 637305, 27066969, 27067049, 27067101, 27067113, 27067115, 179992839, 179993001, 55762149071, 382465573491

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OFFSET

1,2

COMMENTS

Integers k such that A004649(k+1) = 2. - Michel Marcus, Dec 30 2022

LINKS

Table of n, a(n) for n=1..20.

MATHEMATICA

bb={}; Do[If[2==Mod[Prime[n+1], n], bb=Append[bb, n]], {n, 1, 200000}]; bb

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 *)

PROG

(Sage)

def A105287(max) :

terms = []

p = 3

for n in range(1, max+1) :

if (p - 2) % n == 0 : terms.append(n)

p = next_prime(p)

return terms

# Eric M. Schmidt, Feb 05 2013

CROSSREFS

Cf. A004649, A105286, A105288, A105290, A105329, A105451.