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A006596 Numbers n such that (2^{2n+1} - 2^{n+1} + 1)/5 is prime.
(Formerly M1325)
0
2, 5, 6, 14, 21, 26, 141, 278, 281, 306, 345, 1365, 2573, 2661, 4766, 5385 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

REFERENCES

J. Brillhart et al., Factorizations of b^n +- 1. Contemporary Mathematics, Vol. 22, Amer. Math. Soc., Providence, RI, 2nd edition, 1985; and later supplements.

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

LINKS

Table of n, a(n) for n=1..16.

J. Brillhart et al., Factorizations of b^n +- 1, Contemporary Mathematics, Vol. 22, Amer. Math. Soc., Providence, RI, 3rd edition, 2002.

Victor Meally, Letter to N. J. A. Sloane, no date.

S. S. Wagstaff, Jr., The Cunningham Project

MATHEMATICA

For[ i=1, i<=10000, i++, If[ PrimeQ[ ( 2^(2n+1) - 2^(n+1) + 1)/5 ], Print[ n ] ] ]

PROG

(PARI) is(n)=ispseudoprime((2^(2*n+1) - 2^(n+1) + 1)/5) \\ Charles R Greathouse IV, Jun 13 2017

CROSSREFS

Sequence in context: A191120 A245540 A211369 * A000092 A100630 A275839

Adjacent sequences:  A006593 A006594 A006595 * A006597 A006598 A006599

KEYWORD

nonn,hard,more

AUTHOR

N. J. A. Sloane.

EXTENSIONS

More terms from Douglas R. Burke (dburke(AT)nevada.edu)

STATUS

approved

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Last modified March 30 16:16 EDT 2020. Contains 333127 sequences. (Running on oeis4.)