login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo

Please make a donation to keep the OEIS running. We are now in our 56th year. In the past year we added 10000 new sequences and reached almost 9000 citations (which often say "discovered thanks to the OEIS").
Other ways to donate

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A235109 Averages q of twin prime pairs, such that q concatenated to q is also the average of a twin prime pair. 1
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 (list; graph; refs; listen; history; text; internal format)
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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified December 3 14:15 EST 2020. Contains 338906 sequences. (Running on oeis4.)