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A120023 Numbers n such that 2*6^n+1 is prime. 2
0, 1, 2, 3, 4, 10, 11, 17, 20, 28, 41, 48, 57, 58, 59, 71, 208, 972, 993, 1432, 2001, 2175, 2622, 3419, 3720, 4860, 7300, 7402, 14988, 15774, 18510, 22872, 52139, 77028, 149025, 172170, 239699 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

a(1)-a(37) proven prime by the primality proving program LLR. - Robert Price, Jan 08 2016

a(38) > 2.5*10^5. - Robert Price, Jan 08 2016

REFERENCES

If 6^n is of the form T(x,y)=2xy+x+y [A083487] then 2*6^n+1 is not prime. [Vincenzo Librandi, Nov 13 2010]

LINKS

Table of n, a(n) for n=1..37.

MATHEMATICA

Select[Range[0, 2000], PrimeQ[2*6^# + 1] &] (* Vladimir Joseph Stephan Orlovsky, Jan 31 2012 *)

PROG

(PARI) isok(n) = isprime(2*6^n+1); \\ Michel Marcus, Jan 08 2016

CROSSREFS

Cf. A057472, A120024, A205771.

Sequence in context: A202426 A039002 A295393 * A115897 A116019 A259561

Adjacent sequences:  A120020 A120021 A120022 * A120024 A120025 A120026

KEYWORD

nonn

AUTHOR

Pierre CAMI, Jun 04 2006

EXTENSIONS

More terms from Pierre CAMI, Jun 16 2006

a(32)-a(37) from Robert Price, Jan 08 2016

STATUS

approved

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Last modified February 16 04:34 EST 2019. Contains 320140 sequences. (Running on oeis4.)