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.
%I A103858 #27 Jun 20 2025 08:13:34
%S A103858 0,0,2,1,2,2,2,2,4,2,3,4,4,5,5,3,5,3,4,6,5,4,5,6,9,1,4
%N A103858 Number of distinct prime factors of prime(n)! - prime(n)# + 1.
%C A103858 a(27) >= 4. - _Amiram Eldar_, Jan 21 2024
%H A103858 Factordb.com, <a href="http://factordb.com/index.php?query=107%21-107%23%2B1">Status of 107! - 107# + 1</a>.
%H A103858 Reinhard Zumkeller, <a href="/A103855/a103855.txt">prime(n)! - prime(n)# + 1</a>.
%F A103858 a(n) = A001221(A103855(n)).
%t A103858 primorial[n_] := Product[Prime[i], {i, n}]; A103855[n_] := Prime[n]! - primorial[n] + 1; PrimeNu[Array[A103855, 20]] (* _G. C. Greubel_, May 09 2017 *)
%o A103858 (PARI) a(n) = omega(prime(n)! - prod(k=1, n, prime(k)) + 1); \\ _Michel Marcus_, Nov 06 2022
%Y A103858 Cf. A001221, A103855, A103859, A103893.
%K A103858 nonn,more
%O A103858 1,3
%A A103858 _Reinhard Zumkeller_, Feb 20 2005
%E A103858 a(27) from _Jinyuan Wang_, Jun 19 2025