OFFSET
1,4
COMMENTS
For the first 12000 terms the average is ~3.8 with a maximum of 25 at a(11520).
Essentially the same as A095058. - R. J. Mathar, Apr 24 2016
LINKS
Hans Havermann, Table of n, a(n) for n = 1..12000
EXAMPLE
For n=1, m<0, so there are no solutions. For n=2 there is one solution: m=0, yielding prime 2. For n=3, one solution: m=1, yielding prime 5. For n=4 there are two solutions: m=2 and m=1, yielding primes 11 and 13 respectively. The primes so formed are terms of A095078.
MATHEMATICA
Table[Length[Select[Table[2^n - 2^m - 1, {m, 0, n - 2}], PrimeQ[#] & ]], {n, 1, 100}] (* Robert Price, Apr 21 2016 *)
PROG
(Python)
from sympy import isprime
def a(n): return sum(1 for i in range(n-1) if isprime(2**n-1-2**i))
print([a(n) for n in range(1, 81)]) # Michael S. Branicky, Nov 09 2023
CROSSREFS
KEYWORD
nonn
AUTHOR
Hans Havermann, Apr 21 2016
STATUS
approved