%I #12 Oct 03 2021 04:51:54

%S 55,75,141,164,184,199,358,371,380,432,559,702,745,808,825,858,882,

%T 1077,1097,1279,1299,1303,1328,1408,1431,1486,1502,1558,1654,1702,

%U 1724,1744,1768,1820,1835,1873,1901,1905,1953,1977,2050,2148,2216,2220,2267

%N Numbers k such that prime(k), prime(k+1) and prime(k+2) have 10 as a primitive root, but prime(k-1) and prime(k+3) do not.

%C A prime p has 10 as a primitive root iff the length of the period of the decimal expansion of 1/p is p-1.

%H Amiram Eldar, <a href="/A060260/b060260.txt">Table of n, a(n) for n = 1..10000</a>

%t test[p_] := MultiplicativeOrder[10, p]===p-1; Select[Range[2, 2500], test[Prime[ # ]]&&test[Prime[ #+1]]&&test[Prime[ #+2]]&&!test[Prime[ #-1]]&&!test[Prime[ #+3]]&]

%Y The corresponding primes are in A060261.

%Y Cf. A001913, A002371, A060259, A060262.

%K nonn

%O 1,1

%A _Jeff Burch_, Mar 23 2001

%E Edited by _Dean Hickerson_, Jun 17 2002