cp's OEIS Frontend

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

%I A108423 #11 Mar 26 2018 19:52:22
%S A108423 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,
%T A108423 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,
%U A108423 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
%N A108423 a(n) = A108422(n) - A108421(n).
%C A108423 a(A000079(n)) = 0.
%H A108423 Robert Israel, <a href="/A108423/b108423.txt">Table of n, a(n) for n = 2..10000</a>
%p A108423 N:= 200: # to get a(2)..a(N)
%p A108423 Primes:= select(isprime, [seq(i, i=3..2*N-3, 2)]):
%p A108423 Ones:= map(t -> convert(convert(t, base, 2), `+`), Primes):
%p A108423 VL:= Vector(N): VL[2]:= 2:
%p A108423 VH:= Vector(N): VH[2]:= 2:
%p A108423 for i from 1 to nops(Primes) do
%p A108423   p:= Primes[i];
%p A108423   for j from 1 to i do
%p A108423     k:= (p+Primes[j])/2;
%p A108423     if k > N then break fi;
%p A108423     t:= Ones[i]+Ones[j];
%p A108423     if t > VH[k] then VH[k]:= t fi;
%p A108423     if VL[k]=0 or t < VL[k] then VL[k]:= t fi;
%p A108423   od
%p A108423 od:
%p A108423 convert((VH-VL)[2..N], list); # _Robert Israel_, Mar 26 2018
%K A108423 nonn,base
%O A108423 2,9
%A A108423 _Reinhard Zumkeller_, Jun 03 2005