login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A035789 Start of a string of exactly 1 consecutive (but disjoint) pair of twin primes. 16
29, 41, 59, 71, 227, 239, 269, 281, 311, 347, 461, 521, 569, 599, 617, 641, 659, 857, 881, 1091, 1151, 1229, 1277, 1289, 1301, 1319, 1427, 1451, 1607, 1619, 1667, 1697, 1721, 1787, 1997, 2027, 2141, 2237, 2267, 2309, 2339, 2381, 2549, 2591, 2657, 2687 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Lesser of lonely twin primes.

Old Name was: Let P1,P2,..,P6 be any 6 consecutive primes. The sequence consists of those values of P3 for which P2-P1>2, P4-P3=2 and P6-P5>2.

LINKS

Sebastian Petzelberger, Table of n, a(n) for n = 1..10000

Hugo Pfoertner, FORTRAN program: Consecutive pairs of twin primes.

Randall Rathbun, A study of n-twin_prime clusters among prime numbers, Posting to Number Theory List, Nov 19 1998.

EXAMPLE

The first lonely twin primes (A069453) are 29,31 (23 and 37 are non-twin), 41,43 (37 and 47 are non-twin), 59,61 (53 and 67 are non-twin). Of these, the lesser twins are 29,41,59, so this is how the sequence begins.

23, 27, 29, 31, 37, 41: 27-23>2, 31-29=2, 41-37>2; so 29 is in the sequence.

From Hartmut F. W. Hoft, Apr 05 2016: (Start)

The example should read: 19, 23, 29, 31, 37, 41: 23-19>2, 31-29=2, 41-37>2; so 29 is in the sequence.

a(n)=A069453(2n-1), n>=1.

(End)

MATHEMATICA

PrimeNext[n_]:=Module[{k}, k=n+1; While[ !PrimeQ[k], k++ ]; k]; PrimePrev[n_]:=Module[{k}, k=n-1; While[ !PrimeQ[k], k-- ]; k]; lst={}; Do[p=Prime[n]; If[ !PrimeQ[p-2]&&!PrimeQ[p+4]&&PrimeQ[p+2]&&!PrimeQ[PrimePrev[p]-2]&&!PrimeQ[PrimeNext[p+2]+2], AppendTo[lst, p]], {n, 6!}]; lst (* Vladimir Joseph Stephan Orlovsky, Jul 22 2009 *)

(* starting at n=3 would eliminate the first two primality tests, Hartmut F. W. Hoft, Apr 09 2016 *)

CROSSREFS

Cf. A035790, A035791, A035792, A035793, A035794, A035795, A087641.

Cf. A069453, A069455.

Sequence in context: A068480 A161616 A069454 * A080899 A216815 A157141

Adjacent sequences:  A035786 A035787 A035788 * A035790 A035791 A035792

KEYWORD

nonn,easy

AUTHOR

Randall Rathbun, Nov 30 1998

EXTENSIONS

Edited by Hugo Pfoertner, Oct 15 2003

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 May 19 10:36 EDT 2019. Contains 323390 sequences. (Running on oeis4.)