A235109 Averages q of twin prime pairs, such that q concatenated to q is also the average of a twin prime pair.

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

Offset

1,1

Links

Michael G. Kaarhus, Table of n, a(n) for n = 1..770

Example

192 is in this sequence, because 192 is an average of a twin prime pair, and so is 192192.

Prog

(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

Crossrefs

Subsequence of A014574.

Sequence in context: A169738 A063329 A172465 * A039470 A241049 A075296

Adjacent sequences: A235106 A235107 A235108 * A235110 A235111 A235112

Keyword

base,nonn

Author

Michael G. Kaarhus, Jan 03 2014

Status

approved