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 A373098 #47 Jul 06 2024 21:13:24
%S A373098 0,2,8,4,4,0,4,6,8,8,0,8,2,6,6,0,6,4,2,2,0,2,8,4,4,0,4,6,8,8,0,8,2,6,
%T A373098 6,0,6,4,2,2,0,2,8,4,4,0,4,6,8,8,0,8,2,6,6,0,6,4,2,2,0,2,8,4,4,0,4,6,
%U A373098 8,8,0,8,2,6,6,0,6,4,2,2,0,2,8,4,4,0,4,6,8,8,0,8,2,6,6,0,6,4,2,2
%N A373098 Last digit of n*2^n.
%C A373098 Periodic with period 20: [0,2,8,4,4,0,4,6,8,8,0,8,2,6,6,0,6,4,2,2].
%H A373098 <a href="/index/Rec#order_13">Index entries for linear recurrences with constant coefficients</a>, signature (0,1,0,-1,1,1,-1,-1,1,0,-1,0,1).
%F A373098 a(n) = A010879(A036289(n)).
%F A373098 a(n) = A373099(n) - 1.
%F A373098 a(n) = A373100(n) + 1 (n >= 1).
%F A373098 a(n) = 0 if n mod 5 = 0,
%F A373098 2 if n mod 20 = {1, 12, 18, 19},
%F A373098 8 if n mod 20 = {2, 8, 9, 11},
%F A373098 4 if n mod 20 = {3, 4, 6, 17},
%F A373098 6 if n mod 20 = {7, 13, 14, 16}.
%p A373098 a:= n-> n*2&^n mod 10:
%p A373098 seq(a(n), n=0..100);
%t A373098 a[n_] := Mod[n*2^n, 10]
%o A373098 (Python)
%o A373098 def a(n):
%o A373098 return (n * 2**n) % 10
%o A373098 (PARI) a(n,b=10) = lift(n*Mod(2,b)^n) \\ _Hugo Pfoertner_, May 24 2024
%Y A373098 Cf. A010879, A036289.
%Y A373098 Cf. A373099, A373100.
%K A373098 nonn,base,easy
%O A373098 0,2
%A A373098 _Javier Rodríguez Ríos_, May 23 2024