# Greetings from The On-Line Encyclopedia of Integer Sequences! http://oeis.org/

Search: id:a127964
Showing 1-1 of 1

%I A127964 #21 Oct 13 2024 07:08:24
%S A127964 0,1,2,4,5,7,8,10,14,20,29,38,49,62,82,94,98,155,172,349,853,1307,
%T A127964 1768,2902,5249,5344,5638,6194,7238,21367,41668,47683,58618,63514,
%U A127964 69467,70538,133507,134992,187159,493094,2015698
%N A127964 Number of 0's in the binary expansion of A127962(n).
%C A127964 Apparently numbers k such that (2^(2*k+3)+1)/3 is prime. - _James R. Buddenhagen_, Apr 14 2011 [This is true. See the second formula. - _Amiram Eldar_, Oct 13 2024]
%F A127964 a(n) = A023416(A000979(n)). - _Michel Marcus_, Nov 07 2013
%F A127964 a(n) = (A000978(n)-3)/2. - _Amiram Eldar_, Oct 13 2024
%t A127964 b = {}; Do[c = 1 + Sum[2^(2n - 1), {n, 1, x}]; If[PrimeQ[c], AppendTo[b, c]], {x, 0, 1000}]; a = {}; Do[AppendTo[a, FromDigits[IntegerDigits[b[[x]], 2]]], {x, 1, Length[b]}]; d = {}; Do[AppendTo[d, DigitCount[a[[x]], 10, 0]], {x, 1, Length[a]}]; d
%t A127964 (Select[Prime[Range[200]], PrimeQ[(2^# + 1)/3] &] - 3)/2 (* _Amiram Eldar_, Oct 13 2024 *)
%Y A127964 Cf. A000978, A000979, A023416, A127962, A127961, A000979, A000978, A124400, A126614, A127955, A127956, A127957, A127958, A127936.
%K A127964 nonn,base,more,changed
%O A127964 1,3
%A A127964 _Artur Jasinski_, Feb 09 2007
%E A127964 a(22)-a(29) from _Vincenzo Librandi_, Mar 31 2012
%E A127964 a(30)-a(41) from _Amiram Eldar_, Oct 13 2024

# Content is available under The OEIS End-User License Agreement: http://oeis.org/LICENSE