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A073350
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Primes not at the center of a 3 X 3 magic square of primes.
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4
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2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 61, 67, 79, 83, 97, 101, 107, 113, 163, 181, 197, 199, 223, 229, 233, 277, 313, 317, 331, 433, 439, 457, 569, 859
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OFFSET
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1,1
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COMMENTS
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The "magic sum" is always thrice the central entry.
There are no other terms < 5000.
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LINKS
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MAPLE
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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:
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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