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A088878 Prime numbers p such that 3p - 2 is a prime. 45
3, 5, 7, 11, 13, 23, 37, 43, 47, 53, 61, 67, 71, 103, 113, 127, 137, 163, 167, 181, 191, 193, 211, 251, 257, 263, 271, 277, 293, 307, 313, 331, 337, 347, 373, 401, 431, 433, 443, 461, 467, 487, 491, 523, 541, 557, 587, 593, 601, 673, 677, 727, 751, 757, 761 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Indices of semiprime octagonal numbers. - Jonathan Vos Post, Feb 16 2006
Daughter primes of order 1. - Artur Jasinski, Dec 12 2007
A010051(3*a(n)-2) = 1. - Reinhard Zumkeller, Jul 02 2015
REFERENCES
M. Cerasoli, F. Eugeni and M. Protasi, Elementi di Matematica Discreta, Bologna 1988
Emanuele Munarini and Norma Zagaglia Salvi, Matematica Discreta, UTET, CittaStudiEdizioni, Milano 1997
LINKS
Eric Weisstein's World of Mathematics, Octagonal Number.
Eric Weisstein's World of Mathematics, Semiprime.
EXAMPLE
For p = 3, 3p - 2 = 7;
for p = 523, 3p - 2 = 1567.
MATHEMATICA
lst={}; Do[p=Prime[n]; If[PrimeQ[3*p-2], AppendTo[lst, p]], {n, 5!}]; lst (* Vladimir Joseph Stephan Orlovsky, Dec 22 2008 *)
n = 1; a = {}; Do[If[PrimeQ[(Prime[k] + 2n)/(2n + 1)], AppendTo[a, (Prime[k] + 2n)/(2n + 1)]], {k, 1, 500}]; a (* Artur Jasinski, Dec 12 2007 *)
Select[Prime[Range[150]], PrimeQ[3#-2]&] (* Harvey P. Dale, Feb 27 2024 *)
PROG
(Magma) [ p: p in PrimesUpTo(770) | IsPrime(3*p-2) ]; // Klaus Brockhaus, Dec 21 2008
(PARI) list(lim)=select(p->isprime(3*p-2), primes(primepi(lim))) \\ Charles R Greathouse IV, Jul 25 2011
(Haskell)
a088878 n = a088878_list !! (n-1)
a088878_list = filter ((== 1) . a010051' . subtract 2 . (* 3)) a000040_list
-- Reinhard Zumkeller, Jul 02 2015
CROSSREFS
Cf. A259730.
Sequence in context: A350401 A154319 A080114 * A259730 A254673 A343976
KEYWORD
easy,nonn
AUTHOR
Giovanni Teofilatto, Nov 27 2003
EXTENSIONS
Corrected and extended by Ray Chandler, Dec 27 2003
Entry revised by N. J. A. Sloane, Nov 28 2006, Jul 08 2010
STATUS
approved

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Last modified April 12 12:48 EDT 2024. Contains 371635 sequences. (Running on oeis4.)