cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A352083 Numbers k such that (3^k - k^3)/2 is prime.

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%I A352083 #35 Oct 03 2024 23:31:50
%S A352083 5,13,205,409,413,545,88649
%N A352083 Numbers k such that (3^k - k^3)/2 is prime.
%C A352083 All terms must be odd. - _Michael S. Branicky_, Mar 03 2022
%C A352083 No further terms less than 25000. - _Michael S. Branicky_, Mar 04 2022
%e A352083 5 is a term since (3^5 - 5^3)/2 = 59 is prime.
%t A352083 Select[Range[1, 600, 2], PrimeQ[(3^# - #^3)/2] &] (* _Amiram Eldar_, Mar 03 2022 *)
%o A352083 (Sage) for n in srange(1,10000):
%o A352083              if ((3^n-n^3)//2).is_prime():
%o A352083                   print(n)
%o A352083 (PARI) isok(k) = if (denominator(x=(3^k-k^3)/2) == 1, ispseudoprime(x)); \\ _Michel Marcus_, Mar 03 2022
%o A352083 (Python)
%o A352083 from sympy import isprime
%o A352083 def afind(limit):
%o A352083     for k in range(1, limit+1, 2):
%o A352083         if isprime((3**k - k**3)//2):
%o A352083             print(k, end=", ")
%o A352083 afind(1000) # _Michael S. Branicky_, Mar 03 2022
%K A352083 nonn,more
%O A352083 1,1
%A A352083 _Brennan G. Benfield_, Mar 03 2022
%E A352083 a(7) from _Michael S. Branicky_, Oct 03 2024