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A072541
List of pairs of numbers (k, k+4), where k-1 and k+3 are primes.
1
4, 8, 8, 12, 14, 18, 20, 24, 38, 42, 44, 48, 68, 72, 80, 84, 98, 102, 104, 108, 110, 114, 128, 132, 164, 168, 194, 198, 224, 228, 230, 234, 278, 282, 308, 312, 314, 318, 350, 354, 380, 384, 398, 402, 440, 444, 458, 462, 464, 468, 488, 492, 500, 504, 614, 618
OFFSET
1,1
COMMENTS
The puzzle started with a(3): 8, 12, 14, 18, 20, 24, ?.
REFERENCES
Frankfurter Allgemeine Sonntagszeitung, Jul 28, 2002, "Koennen Sie folgen?", p. 56.
LINKS
FORMULA
a(2*n-1) = A023200(n)+1, a(2*n) = A023200(n)+5, n>0.
MATHEMATICA
Flatten[{#, #+4}&/@Select[Range[700], AllTrue[#+{-1, 3}, PrimeQ]&]] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, Jul 22 2014 *)
PROG
(Haskell)
import Data.List (transpose)
a072541 n = a072541_list !! (n-1)
a072541_list = concat $ transpose
[map (+ 1) a023200_list, map (+ 5) a023200_list]
-- Reinhard Zumkeller, Aug 01 2014
CROSSREFS
Cf. A023200.
Sequence in context: A272812 A273207 A145154 * A141719 A098352 A273395
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Aug 04 2002
STATUS
approved