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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
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