A108423 - OEIS

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

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OFFSET

2,9

COMMENTS

a(A000079(n)) = 0.

LINKS

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

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:

convert((VH-VL)[2..N], list); # Robert Israel, Mar 26 2018

CROSSREFS

Sequence in context: A226289 A107063 A290453 * A361154 A208568 A193804

Adjacent sequences: A108420 A108421 A108422 * A108424 A108425 A108426

KEYWORD

nonn,base

AUTHOR

Reinhard Zumkeller, Jun 03 2005

STATUS

approved