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A061422 Numbers n such that 2^(n-1) + n is prime. 3
1, 3, 7, 237, 1885, 51381, 75765 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

No other terms below 300000. - Giovanni Resta, Nov 12 2012

a(8) > 500000. - Robert Price, May 24 2014

REFERENCES

J.-M. De Koninck, Ces nombres qui nous fascinent, Entry 237, p. 66, Ellipses, Paris 2008.

LINKS

Table of n, a(n) for n=1..7.

K. S. Brown, The Sum of the Prime Factors of N. MathPages.com

PROG

(PARI) is(n)=isprime(2^(n-1)+n) \\ Charles R Greathouse IV, May 22 2017

CROSSREFS

Cf. A061421.

Equals A100359(n) + 1.

Sequence in context: A132564 A057619 A179859 * A206333 A088097 A064774

Adjacent sequences:  A061419 A061420 A061421 * A061423 A061424 A061425

KEYWORD

hard,nonn

AUTHOR

Jason Earls (zevi_35711(AT)yahoo.com), May 02 2001

EXTENSIONS

H. Zeisel found the probable prime 1885. - Benoit Cloitre, Jun 03 2002

New term 51381 from Nuutti Kuosa (see MathPages link). - Max Alekseyev, Feb 08 2009

Deleted an incorrect conjecture. - N. J. A. Sloane, Dec 27 2009

a(7) from Giovanni Resta, Nov 12 2012

STATUS

approved

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Last modified June 25 20:26 EDT 2017. Contains 288730 sequences.