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.

A354226 a(n) is the number of distinct prime factors of (p^p - 1)/(p - 1) where p = prime(n).

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%I A354226 #71 Jan 23 2023 14:23:42
%S A354226 1,1,2,2,2,3,3,1,4,7,1,7,5,3,3,5,3,4,6,4,10,5,4,6,6,9,5,4,5,8,6,4,11
%N A354226 a(n) is the number of distinct prime factors of (p^p - 1)/(p - 1) where p = prime(n).
%C A354226 a(34) > 3, and depends on the full factorization of the 296-digit composite number (139^139 - 1)/138. - _Tyler Busby_, Jan 22 2023
%C A354226 Sequence continues as ?, 8, ?, 5, 8, 4, 5, ?, 8, ?, 8, 7, 6, 3, 3, ..., where ? represents uncertain terms. - _Tyler Busby_, Jan 22 2023
%H A354226 factordb, <a href="http://factordb.com/index.php?query=(139^139-1)/138">Status of (139^139 - 1)/138</a>.
%F A354226 a(n) = A001221(A001039(n)).
%e A354226 a(3)=2, since (5^5 - 1)/(5 - 1) = 11*71.
%o A354226 (PARI) a(n) = my(p=prime(n)); omega((p^p-1)/(p-1)); \\ _Michel Marcus_, May 22 2022
%o A354226 (Python)
%o A354226 from sympy import factorint, prime
%o A354226 def a(n): p = prime(n); return len(factorint((p**p-1)//(p-1)))
%o A354226 print([a(n) for n in range(1, 12)]) # _Michael S. Branicky_, May 23 2022
%Y A354226 Cf. A000040, A001039, A001221, A088790, A125135, A212552, A214812.
%K A354226 nonn,more
%O A354226 1,3
%A A354226 _Luis H. Gallardo_, May 20 2022
%E A354226 a(18)-a(33) from _Amiram Eldar_, May 20 2022