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 A060377 #23 Sep 14 2024 13:26:08 %S A060377 3,9,6561, %T A060377 11790184577738583171520872861412518665678211592275841109096961 %N A060377 Pepin's test numbers. %C A060377 Next two terms have 15635 and 1024610093 digits respectively. [Corrected by _Michael S. Branicky_ and _Sean A. Irvine_, Nov 12 2022] %H A060377 C. K. Caldwell, <a href="https://t5k.org/glossary/page.php?sort=PepinsTest">Pepin's Test</a>. %F A060377 a(n) = 3^((F(n)-1)/2) where F(n) is a Fermat number (A000215). %e A060377 a(1) = 3^((F(1)-1)/2) = 3^((5-1)/2) = 3^2 = 9. %t A060377 A000215[n_]:=2^(2^n)+1; a[n_]:=3^((A000215[n]-1)/2); Array[a,4,0] (* _Stefano Spezia_, Sep 14 2024 *) %o A060377 (Python) %o A060377 def a(n): return 3**(2**(2**n-1)) %o A060377 print([a(n) for n in range(4)]) # _Michael S. Branicky_, Nov 12 2022 %Y A060377 Cf. A000215. %K A060377 nonn %O A060377 0,1 %A A060377 _Jason Earls_, Apr 02 2001 %E A060377 Corrected offset, formula and example _Harry J. Smith_, Jul 04 2009