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A355142
a(n) = 33648*3^n - 1.
0
33647, 100943, 302831, 908495, 2725487, 8176463, 24529391, 73588175, 220764527, 662293583, 1986880751, 5960642255, 17881926767, 53645780303, 160937340911, 482812022735, 1448436068207, 4345308204623, 13035924613871, 39107773841615, 117323321524847, 351969964574543
OFFSET
0,1
COMMENTS
For n > 0, this is the trajectory of 100943 under the map x -> 3*x+2.
100943 is the least starting value > 0 where the trajectory under the map in the previous comment does not reach a prime after a small number of steps.
Are there any primes > 100943 in the sequence (cf. A354747 and A354748)?
FORMULA
G.f.: (33647 - 33645*x)/((1 - x)*(1 - 3*x)). - Stefano Spezia, Jun 21 2022
MATHEMATICA
33648*3^Range[0, 30]-1 (* or *) LinearRecurrence[{4, -3}, {33647, 100943}, 30] (* Harvey P. Dale, Mar 03 2023 *)
PROG
(PARI) a(n) = 33648*3^n-1
(Python)
a = [33647]; [a.append(3*a[-1]+2) for n in range(21)]
print(a) # Michael S. Branicky, Jun 20 2022
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Felix Fröhlich, Jun 20 2022
STATUS
approved