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A057732 Numbers n such that 2^n + 3 is prime. 19
1, 2, 3, 4, 6, 7, 12, 15, 16, 18, 28, 30, 55, 67, 84, 228, 390, 784, 1110, 1704, 2008, 2139, 2191, 2367, 2370, 4002, 4060, 4062, 4552, 5547, 8739, 17187, 17220, 17934, 20724, 22732, 25927, 31854, 33028, 35754, 38244, 39796, 40347, 55456, 58312, 122550, 205962, 235326, 363120, 479844, 685578 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Some of the larger entries may only correspond to probable primes.

REFERENCES

Mike Oakes, posting to primenumbers(AT)yahoogroups.com on Jul 08 2001

LINKS

Table of n, a(n) for n=1..51.

Henri & Renaud Lifchitz, PRP Records.

MATHEMATICA

Clear[f, n]; f[n_]:=PrimeQ[2^n+3]; lst={}; Do[If[f[n], AppendTo[lst, n]], {n, 2000}]; lst (* Vladimir Joseph Stephan Orlovsky, Aug 02 2009 *)

PROG

(PARI) j=[]; for(n=1, 2200, if(isprime(2^n+3), j=concat(j, n))); j

CROSSREFS

Cf. A050414 (2^n-3 is prime).

Sequence in context: A057128 A018534 A018276 * A092591 A039947 A096477

Adjacent sequences:  A057729 A057730 A057731 * A057733 A057734 A057735

KEYWORD

nice,nonn

AUTHOR

G. L. Honaker, Jr., Oct 29 2000

EXTENSIONS

More terms from Jason Earls (zevi_35711(AT)yahoo.com), Jul 18 2001 and _Mike Oakes, Jul 28 2001

Terms 47 to 50 from Donovan Johnson 2006, verified by Paul Bourdelais, Mar 22 2012

a(51) is a probable prime based on trial factoring to 1E9 and PRP testing base 3,5,7 (PFGW v3.3.1). Discovered by Paul Bourdelais, Apr 09 2012

STATUS

approved

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Last modified April 17 11:46 EDT 2014. Contains 240635 sequences.