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A235109
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Averages q of twin prime pairs, such that q concatenated to q is also the average of a twin prime pair.
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1
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42, 102, 108, 180, 192, 270, 312, 420, 522, 660, 822, 882, 1230, 1482, 4242, 4788, 8820, 10332, 11550, 13692, 14550, 14562, 14868, 15732, 17910, 18522, 20550, 21648, 22620, 23670, 23832, 26262, 27738, 35838, 38922, 39042, 40128, 42018, 43962, 44532, 46440
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OFFSET
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1,1
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LINKS
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EXAMPLE
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192 is in this sequence, because 192 is an average of a twin prime pair, and so is 192192.
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PROG
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(Maxima) q:0$ for n:1 thru 800 step 0 do (q:q+6, if(primep(q-1) and primep(q+1)) then (b:concat(q, q), c:eval_string(b), if(primep(c-1) and primep(c+1)) then (if c>341550071728321 then (print("# ", c, " not determ."), n:5000), print(n, ", ", q), n:n+1 ) ) )$
(PARI) cat(n)=eval(concat(Str(n), n))
istwin(n)=n%6==5&&isprime(n)&&isprime(n+2)
v=List(); p=2; forprime(q=3, 1e10, if(q-p==2 && istwin(cat(p+1)-1), listput(v, p+1); if(#v==10^4, return)); p=q) \\ Charles R Greathouse IV, Jan 03 2014
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CROSSREFS
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KEYWORD
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base,nonn
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AUTHOR
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STATUS
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approved
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