cp's OEIS Frontend

A073350 Primes not at the center of a 3 X 3 magic square of primes.

%I A073350 #16 Feb 16 2016 17:39:40
%S A073350 2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,61,67,79,83,97,101,107,
%T A073350 113,163,181,197,199,223,229,233,277,313,317,331,433,439,457,569,859
%N A073350 Primes not at the center of a 3 X 3 magic square of primes.
%C A073350 The "magic sum" is always thrice the central entry.
%C A073350 There are no other terms < 5000.
%C A073350 There are no other terms < 100000. - _Robert Israel_, Feb 16 2016
%H A073350 <a href="/index/Mag#magic">Index entries for sequences related to magic squares</a>
%p A073350 N:= 10000: # to get all terms <= N
%p A073350 P:= select(isprime,{seq(p,p=3..2*N,2)}):
%p A073350 count:= 1:
%p A073350 A[count]:= 2:
%p A073350 for ic from 1 while P[ic] <= N do
%p A073350    c:= P[ic];
%p A073350    V:= map(`-`,P[ic+1..-1],c) intersect map(t -> c-t, P[1..ic-1]);
%p A073350    nv:= nops(V);
%p A073350    VV:= {seq(seq(V[j]-V[i],j=i+1..nv),i=1..nv-1)} intersect V;
%p A073350    nvv:= nops(VV);
%p A073350    found:= false;
%p A073350    for ia from 1 to nvv while not found do
%p A073350      a:= VV[ia];
%p A073350      for ib from ia+1 to nvv while VV[ib] < c - a do
%p A073350        b:= VV[ib];
%p A073350        if b <> 2*a and {c-a-b,c-a+b,c-b+a,c+a+b} subset P then
%p A073350           found:= true;
%p A073350           break
%p A073350        fi
%p A073350      od
%p A073350    od:
%p A073350    if not found then
%p A073350      count:= count+1;
%p A073350      A[count]:= c;
%p A073350    fi
%p A073350 od:
%p A073350 seq(A[i],i=1..count); # _Robert Israel_, Feb 16 2016
%Y A073350 Cf. A073473. A magic square with 59 at center is given in A024351.
%K A073350 nonn
%O A073350 1,1
%A A073350 _David W. Wilson_, Aug 25 2002