login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A130327 Least prime p such that 3*p*2^n-1 and 3*p*2^n+1 are twin primes. 4
2, 2, 5, 3, 5, 2, 11, 3, 19, 17, 5, 113, 59, 317, 331, 307, 241, 2, 829, 23, 149, 127, 11, 3023, 1091, 787, 971, 1523, 2741, 727, 1051, 227, 211, 727, 89, 1163, 71, 367, 1031, 577, 89, 1213, 1151, 3, 1021, 283, 2699, 4933, 59, 647, 709 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,1
LINKS
EXAMPLE
3*2*2^0-1=5, 3*2*2^0+1=7: 5 and 7 are twin primes so for n=0 p=2.
3*2*2^1-1=11, 3*2*2^1+1=13: 11 and 13 are twin primes so for n=1 p=2.
MATHEMATICA
lpp[n_]:=Module[{p=2}, While[!AllTrue[3p 2^n+{1, -1}, PrimeQ], p=NextPrime[p]]; p]; Array[lpp, 60, 0] (* Harvey P. Dale, May 13 2022 *)
PROG
(PARI) a(n) = my(p=2); while (!(isprime(q=3*p*2^n-1) && isprime(q+2)), p=nextprime(p+1)); p; \\ Michel Marcus, Sep 23 2019
CROSSREFS
Sequence in context: A128134 A157223 A174608 * A224361 A341443 A224166
KEYWORD
nonn
AUTHOR
Pierre CAMI, May 24 2007
STATUS
approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified April 22 00:17 EDT 2024. Contains 371886 sequences. (Running on oeis4.)