OFFSET
1,1
COMMENTS
The "magic sum" is always thrice the central entry.
There are no other terms < 5000.
There are no other terms < 100000. - Robert Israel, Feb 16 2016
MAPLE
N:= 10000: # to get all terms <= N
P:= select(isprime, {seq(p, p=3..2*N, 2)}):
count:= 1:
A[count]:= 2:
for ic from 1 while P[ic] <= N do
c:= P[ic];
V:= map(`-`, P[ic+1..-1], c) intersect map(t -> c-t, P[1..ic-1]);
nv:= nops(V);
VV:= {seq(seq(V[j]-V[i], j=i+1..nv), i=1..nv-1)} intersect V;
nvv:= nops(VV);
found:= false;
for ia from 1 to nvv while not found do
a:= VV[ia];
for ib from ia+1 to nvv while VV[ib] < c - a do
b:= VV[ib];
if b <> 2*a and {c-a-b, c-a+b, c-b+a, c+a+b} subset P then
found:= true;
break
fi
od
od:
if not found then
count:= count+1;
A[count]:= c;
fi
od:
seq(A[i], i=1..count); # Robert Israel, Feb 16 2016
CROSSREFS
KEYWORD
nonn
AUTHOR
David W. Wilson, Aug 25 2002
STATUS
approved