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 A345420 #13 Jul 01 2021 23:40:56 %S A345420 1,-1,0,3,-2,-5,7,4,-9,6,-6,15,-8,-17,19,-21,12,-12,27,-14,-29,16,-33, %T A345420 18,39,-20,-41,43,22,-45,51,-26,55,28,30,-30,63,-65,67,-69,36,-36,-38, %U A345420 -77,79,40,-42,-89,91,46,-93,48,-48,-50,103,-105,54,-54,111,-56,-113,-117,123,-62 %N A345420 Row 3 of array in A345417. %o A345420 (Python) %o A345420 from sympy.core.numbers import igcdex %o A345420 from sympy import prime %o A345420 def A345420(n): return igcdex(5, prime(n))[0] # _Chai Wah Wu_, Jul 01 2021 %Y A345420 Cf. A345417-A345422. %K A345420 sign %O A345420 1,4 %A A345420 _N. J. A. Sloane_, Jun 19 2021