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A234098 Primes of the form (p*q + 1)/2, where p and q are distinct primes. 4
11, 17, 29, 43, 47, 67, 71, 73, 89, 101, 103, 107, 109, 127, 151, 191, 197, 223, 227, 241, 251, 269, 277, 283, 317, 349, 359, 373, 397, 409, 433, 457, 461, 467, 487, 521, 541, 569, 571, 631, 643, 647, 659, 673, 701, 709, 719, 733, 739, 751, 757, 769, 821 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
EXAMPLE
11 = (3*7 + 1)/2, 17 = (5*7 + 1)/2.
MATHEMATICA
t = Select[Range[1, 7000, 2], Map[Last, FactorInteger[#]] == Table[1, {2}] &]; Take[(t + 1)/2, 120] (* A234096 *)
v = Flatten[Position[PrimeQ[(t + 1)/2], True]] ; w = Table[t[[v[[n]]]], {n, 1, Length[v]}] (* A233562 *)
(w + 1)/2 (* A234098 *) (* Peter J. C. Moses, Dec 23 2013 *)
PROG
(Haskell)
a234098 n = a234098_list !! (n-1)
a234098_list = filter ((== 1) . a010051') $
map ((flip div 2) . (+ 1)) a046388_list
-- Reinhard Zumkeller, Jan 02 2014
CROSSREFS
Sequence in context: A330410 A111255 A060213 * A153502 A249377 A211486
KEYWORD
nonn,easy
AUTHOR
Clark Kimberling, Dec 27 2013
STATUS
approved

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Last modified March 28 20:05 EDT 2024. Contains 371254 sequences. (Running on oeis4.)