A048797 -id:A048797 - cp's OEIS frontend

A123921 Primes of form p*q - 2 where p and q are consecutive primes.

13, 25589, 47051, 67589, 136889, 313589, 960389, 1005971, 1932017, 2301251, 2362331, 6100889, 6310061, 6901091, 7745051, 8236817, 9332987, 10956089, 13104389, 16850987, 19009589, 19201841, 19386371, 19998701, 20566079

Offset: 1

Ville Saalo (vsaalo(AT)iki.fi), Nov 19 2006

			211*223-2 = 47051.

T. D. Noe, Table of n, a(n) for n = 1..1000

Cf. A048797, A048880.

a123921 n = a123921_list !! (n-1)
a123921_list = filter ((== 1) . a010051) $
   map (flip (-) 2) $ zipWith (*) a000040_list (tail a000040_list)
-- Reinhard Zumkeller, Nov 11 2011

with (numtheory): for n from 1 to 1000 do if (tau(ithprime(n)*ithprime(n+1)-2)=2) then print(ithprime(n), ithprime(n+1), ithprime(n)*ithprime(n+1)-2); fi; od;

Select[Times@@@Partition[Prime[Range[1500]],2,1]-2,PrimeQ] (* Harvey P. Dale, Feb 23 2012 *)

p=2; forprime(q=3,1e5, if(isprime(t=p*q-2), print1(t", ")); p=q) \\ Charles R Greathouse IV, Apr 29 2015

A093706 Primes p such that (pp'-1)/2 is prime, where p' denotes the next prime after p.

Original entry on oeis.org

3, 5, 11, 29, 41, 71, 137, 281, 461, 599, 641, 787, 827, 881, 1091, 1129, 1301, 1409, 1607, 1627, 1951, 2129, 2267, 2357, 2381, 2557, 2687, 2887, 2917, 3469, 3527, 3557, 3581, 3967, 4127, 4229, 4337, 4547, 4889, 5009, 5309, 5741, 6131, 6133, 6247, 6343

Offset: 1

Robert G. Wilson v, Apr 10 2004

nonn

Hugo Pfoertner, Table of n, a(n) for n = 1..10000

Cf. A048797.

Prime[ Select[ Range[850], PrimeQ[(Prime[ # ]Prime[ # + 1] - 1)/2] &]]
Transpose[Select[Partition[Prime[Range[900]],2,1],PrimeQ[ (Times@@#- 1)/2]&]][[1]] (* Harvey P. Dale, Sep 17 2011 *)

isA093706(n) = if(n<3,0,isprime(n) && isprime((n*nextprime(n+1)-1)/2)) \\ Michael B. Porter, Dec 15 2009

cp's OEIS Frontend

A123921 Primes of form p*q - 2 where p and q are consecutive primes.

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