OFFSET
1,1
COMMENTS
Odd primes with Hamming weight (A000120) at most three. - Jeppe Stig Nielsen, Dec 09 2020
LINKS
T. D. Noe, Table of n, a(n) for n=1..1000
EXAMPLE
41 = 2^5 + 2^3 + 1, hence 41 is in the sequence.
MAPLE
k := 0:for i from 1 to 140 do for j from i to 140 do if isprime(2^i+2^j+1) then k := k+1:c[k] := 2^i+2^j+1:fi:od:od:sort([3, seq(c[i], i=1..k)]); # gives all terms up to 2^140
MATHEMATICA
f[x_, y_]:=2^x+2^y+1; imax=20; lst={}; Do[p=f[x, y]; If[p<2^imax+3 && PrimeQ[p], AppendTo[lst, p]], {y, 0, imax}, {x, 0, y}]; Union[lst] (* Vladimir Joseph Stephan Orlovsky, Apr 08 2011 *)
Union[Select[Total/@(2^#&/@Union[Sort[Tuples[Range[0, 20], 2]]])+1, PrimeQ]] (* Harvey P. Dale, Jun 06 2020 *)
PROG
(PARI) for(n=1, 300, if(sum(i=0, n, sum(j=0, i, if(2^i+2^j+1-prime(n), 0, 1)))>0, print1(prime(n), ", ")))
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, May 14 2002
EXTENSIONS
More terms from Sascha Kurz, Aug 15 2002
STATUS
approved