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A093625 Primes of the form (3^n+1)/2. 2
2, 5, 41, 21523361, 926510094425921, 1716841910146256242328924544641 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Primes can only occur for n=2^k. The next term (if it exists) has k>=21 (i.e. more than 10^6 decimal digits). - Don Reble (djr(AT)nk.ca), Apr 28 2004. [For the latest results about the search, see A171381. - N. J. A. Sloane, Jun 14 2010]

LINKS

Table of n, a(n) for n=1..6.

EXAMPLE

a(3)=41 because it can be written as (3^4+1)/2=82/2.

CROSSREFS

A171381 is the main entry for this sequence. Cf. also A138083.

Sequence in context: A076725 A059917 A255963 * A042447 A176266 A075872

Adjacent sequences:  A093622 A093623 A093624 * A093626 A093627 A093628

KEYWORD

nonn,hard

AUTHOR

Hugo Pfoertner, Apr 19 2004

EXTENSIONS

Erroneous terms deleted by N. J. A. Sloane, Jun 14 2010

STATUS

approved

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Last modified May 27 07:41 EDT 2017. Contains 287198 sequences.