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A177679 Numbers k such that 30*k and 60*k are both the average of twin prime pairs. 1
1, 22, 27, 71, 85, 111, 113, 195, 209, 351, 1106, 1387, 1471, 1785, 1848, 1911, 2128, 2170, 2346, 2366, 2409, 2470, 2492, 2626, 2689, 2731, 2918, 3108, 3410, 3849, 4159, 4466, 4565, 5214, 5382, 5615, 6117, 6161, 6559, 7035, 7063, 7349, 7469, 7798, 7923 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
FORMULA
a(n) = A066388(n+1)/30.
EXAMPLE
a(1)=1 because 30*1-1=29, 30*1+1=31, 60*1-1=59 and 60*1+1=61 are all twin primes.
MATHEMATICA
Select[Range[8000], AllTrue[{30#-1, 30#+1, 60#-1, 60#+1}, PrimeQ] &] (* Amiram Eldar, Dec 20 2019 *)
PROG
(Magma) [k:k in [1..8000]|IsPrime(30*k-1) and IsPrime(30*k+1) and IsPrime(60*k-1) and IsPrime(60*k+1)]; // Marius A. Burtea, Dec 20 2019
CROSSREFS
Cf. A014574.
Sequence in context: A038355 A043128 A043908 * A276184 A336585 A255222
KEYWORD
nonn
AUTHOR
EXTENSIONS
Corrected (185 replaced by 195, 2718 replaced by 2918, 2731 inserted etc.) by R. J. Mathar, May 15 2010
STATUS
approved

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Last modified March 29 09:14 EDT 2024. Contains 371268 sequences. (Running on oeis4.)