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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 (list; graph; refs; listen; history; text; internal format)
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

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

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

Adjacent sequences:  A072538 A072539 A072540 * A072542 A072543 A072544

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Aug = 04 2002

STATUS

approved

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Last modified June 25 22:35 EDT 2019. Contains 324364 sequences. (Running on oeis4.)