OFFSET
1,3
COMMENTS
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]
FORMULA
a(n) = (A000978(n)-3)/2. - Amiram Eldar, Oct 13 2024
MATHEMATICA
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
(Select[Prime[Range[200]], PrimeQ[(2^# + 1)/3] &] - 3)/2 (* Amiram Eldar, Oct 13 2024 *)
CROSSREFS
KEYWORD
nonn,base,more,changed
AUTHOR
Artur Jasinski, Feb 09 2007
EXTENSIONS
a(22)-a(29) from Vincenzo Librandi, Mar 31 2012
a(30)-a(41) from Amiram Eldar, Oct 13 2024
STATUS
approved