A108423 a(n) = A108422(n) - A108421(n).

0, 0, 0, 1, 0, 1, 0, 1, 2, 2, 1, 0, 1, 2, 0, 3, 2, 2, 2, 3, 3, 3, 1, 2, 2, 4, 1, 3, 3, 3, 0, 1, 0, 4, 3, 3, 4, 5, 2, 3, 4, 2, 3, 5, 4, 4, 1, 0, 4, 4, 3, 4, 4, 4, 2, 4, 2, 4, 3, 2, 1, 3, 0, 3, 2, 5, 4, 4, 5, 4, 3, 4, 4, 5, 3, 5, 5, 5, 2, 3, 4, 4, 4, 5, 3, 6, 1, 3, 5, 3, 1, 5, 4, 2, 1, 4, 4, 6, 4, 4, 4, 6, 2, 6, 4

Offset: 2

Author

Reinhard Zumkeller, Jun 03 2005

Keywords

• nonn
• base

Comments

a(A000079(n)) = 0.

Links

• Robert Israel, Table of n, a(n) for n = 2..10000

Programs

Maple

N:= 200: # to get a(2)..a(N)
Primes:= select(isprime, [seq(i, i=3..2*N-3, 2)]):
Ones:= map(t -> convert(convert(t, base, 2), `+`), Primes):
VL:= Vector(N): VL[2]:= 2:
VH:= Vector(N): VH[2]:= 2:
for i from 1 to nops(Primes) do
  p:= Primes[i];
  for j from 1 to i do
    k:= (p+Primes[j])/2;
    if k > N then break fi;
    t:= Ones[i]+Ones[j];
    if t > VH[k] then VH[k]:= t fi;
    if VL[k]=0 or t < VL[k] then VL[k]:= t fi;
  od
od:
convert((VH-VL)[2..N], list); # Robert Israel, Mar 26 2018