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.
is(k) = isprime(k!+(k!/2)+1);
3!^2 / 2 + 1 = 6^2/2 + 1 = 19, a prime number, so 3 is a term.
isok(k) = (k>1) && isprime(k!^2 / 2 + 1); \\ Michel Marcus, Jan 15 2023
4 is a term, because 4!^2 + 3!^2 + 1 = 576 + 36 + 1 = 613 is a prime number.
is(k) = isprime((k!^2)+((k-1)!)^2+1);
from itertools import count, islice from sympy import isprime def A374901_gen(): # generator of terms f = 1 for k in count(1): if isprime((k**2+1)*f+1): yield k f *= k**2 A374901_list = list(islice(A374901_gen(),10)) # Chai Wah Wu, Oct 02 2024
14 is a term, because 14!^2 + 13!^2 - 1 = 7600054456551997440000 + 38775788043632640000 - 1 = 7638830244595630079999 is a prime number.
select(k -> isprime((k^2+1)*((k-1)!)^2-1), [$1..1000]); # Robert Israel, Aug 12 2024
is(k) = isprime(k!^2 + (k-1)!^2 - 1);
from itertools import count, islice from sympy import isprime def A375310_gen(): # generator of terms f = 1 for k in count(1): if isprime((k**2+1)*f-1): yield k f *= k**2 A375310_list = list(islice(A375310_gen(),6)) # Chai Wah Wu, Oct 02 2024
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