A247681 - OEIS

%I #27 Sep 02 2020 03:06:58

%S 1,55,91,145,217,235,253,289,325,343,361,415,451,469,505,559,595,649,

%T 667,685,703,721,775,793,847,865,901,955,973,1027,1045,1081,1099,1135,

%U 1189,1207,1225,1243,1261,1315,1333,1351,1369,1387,1405

%N Odd nonprimes congruent to 1 modulo 9.

%C Subsequence of A017173.

%H Odimar Fabeny, <a href="/A247681/b247681.txt">Table of n, a(n) for n = 1..10000</a>

%t Select[18Range[0, 99] + 1, Not[PrimeQ[#]] &] (* _Alonso del Arte_, Sep 25 2014 *)

%t Select[Range[1,1500,18],!PrimeQ[#]&] (* _Harvey P. Dale_, Mar 07 2018 *)

%o (PARI) lista(nn) = {forcomposite(n=1, nn, if ((n % 2) && ((n % 9) == 1), print1(n, ", ")); ); } \\ _Michel Marcus_, Sep 22 2014

%Y Cf. A017173, A247676, A247678, A247679, A247682, A247683, A247900 (first differences).

%K nonn,easy

%O 1,2

%A _Odimar Fabeny_, Sep 22 2014