OFFSET
0,1
COMMENTS
LINKS
Robert Israel, Table of n, a(n) for n = 0..605
EXAMPLE
a(3) = 180 because 180 is the average of twin primes 179 and 181, is the sum of two such averages in exactly 3 ways: 180 = 30 + 150 = 42 + 138 = 72 + 108, and no smaller average of twin primes works.
MAPLE
M:= select(t -> isprime(t+1) and isprime(t-1), {seq(i, i=6..10^6, 6)}):V:= Vector(max(M)/6):for i from 2 to nops(M) do
for j from 1 to i-1 do
s:= M[i]+M[j];
if s > 10^6 then break fi;
if member(s, M) then
V[s/6]:= V[s/6]+1;
fi
od od:
A:= Array(0..100): A[0]:= 4:
for m in M do
v:= V[m/6];
if v <= 100 and A[v] = 0 then A[v]:= m fi
od:
convert(A, list);
CROSSREFS
KEYWORD
nonn
AUTHOR
J. M. Bergot and Robert Israel, Nov 17 2022
STATUS
approved