A062061 - OEIS

%I #12 Apr 23 2022 13:16:58

%S 2,4,70,516,174080,292050,637320,687105342,14342420320,214517880600

%N Numbers k such that prime(k)+1 divides k^2.

%C a(9) > 3*10^9. - _Donovan Johnson_, Oct 14 2009

%C a(11) > 3*10^11. - _Giovanni Resta_, Apr 15 2017

%e Prime(4)+1 = 7+1 divides 4^2, so 4 is a term of the sequence.

%t Select[Range[10^6], Mod[ #^2, Prime[ # ] + 1] == 0 &]

%t Select[Range[640000],PowerMod[#,2,Prime[#]+1]==0&] (* The program generates the first seven terms of the sequence. To generate more, increase the Range constant. *) (* _Harvey P. Dale_, Apr 23 2022 *)

%o (PARI) isok(n) = n^2 % (prime(n)+1) == 0; \\ _Michel Marcus_, Apr 15 2017

%Y Cf. A045924, A061437.

%K nonn

%O 1,1

%A _Joseph L. Pe_, Feb 13 2002

%E a(8) from _Donovan Johnson_, Oct 14 2009

%E a(9)-a(10) from _Giovanni Resta_, Apr 15 2017