cp's OEIS Frontend

A236204 Numbers not divisible by 2, 3 or 11.

%I A236204 #28 Oct 23 2020 03:27:50
%S A236204 1,5,7,13,17,19,23,25,29,31,35,37,41,43,47,49,53,59,61,65,67,71,73,79,
%T A236204 83,85,89,91,95,97,101,103,107,109,113,115,119,125,127,131,133,137,
%U A236204 139,145,149,151,155,157,161,163,167,169,173,175,179,181,185,191,193,197,199,203,205
%N A236204 Numbers not divisible by 2, 3 or 11.
%C A236204 All primes except 2, 3 and 11 are in this sequence. Any product of terms is also a term in the sequence. - _Alonso del Arte_, Feb 04 2014
%C A236204 Also integers n such that least prime factor of 32^n-1 is 31. - _Giovanni Resta_, Mar 22 2014
%C A236204 Numbers coprime to 66. The asymptotic density of this sequence is 10/33. - _Amiram Eldar_, Oct 23 2020
%H A236204 Vincenzo Librandi, <a href="/A236204/b236204.txt">Table of n, a(n) for n = 1..1000</a>
%H A236204 <a href="/index/Rec#order_21">Index entries for linear recurrences with constant coefficients</a>, signature (1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,-1).
%F A236204 a(n) = a(n-1) + a(n-20) - a(n-21). - _Charles R Greathouse IV_, Mar 26 2014
%F A236204 For n > 20, a(n) = a(n - 20) + 66. - _Zak Seidov_, Mar 27 2014
%F A236204 G.f.: x*(x^20 + 4*x^19 + 2*x^18 + 6*x^17 + 4*x^16 + 2*x^15 + 4*x^14 + 2*x^13 + 4*x^12 + 2*x^11 + 4*x^10 + 2*x^9 + 4*x^8 + 2*x^7 + 4*x^6 + 2*x^5 + 4*x^4 + 6*x^3 + 2*x^2 + 4*x + 1)/(x^21 - x^20 - x + 1). - _Chai Wah Wu_, Aug 03 2020
%t A236204 Select[2Range[125] - 1, GCD[#, 66] == 1 &] (* _Alonso del Arte_, Feb 04 2014 *)
%o A236204 (PARI) is(n)=gcd(n,66)==1 \\ _Charles R Greathouse IV_, Mar 26 2014
%Y A236204 Cf. A235583.
%K A236204 nonn,easy
%O A236204 1,2
%A A236204 _Oleg P. Kirillov_, Jan 20 2014