cp's OEIS Frontend

A229784 a(n) = (1^1^1 + 2^2^2 . . . + n^n^n) mod 10.

%I A229784 #21 Oct 20 2023 11:12:04
%S A229784 0,1,7,4,0,5,1,4,0,9,9,0,6,9,5,0,6,3,9,8,8,9,5,2,8,3,9,2,8,7,7,8,4,7,
%T A229784 3,8,4,1,7,6,6,7,3,0,6,1,7,0,6,5,5,6,2,5,1,6,2,9,5,4,4,5,1,8,4,9,5,8,
%U A229784 4,3,3,4,0,3,9,4,0,7,3,2,2,3,9,6,2,7,3,6,2,1,1,2,8,1,7,2,8,5,1,0,0,1,7,4,0,5,1,4,0,9,9
%N A229784 a(n) = (1^1^1 + 2^2^2 . . . + n^n^n) mod 10.
%C A229784 The last digit of 1^1^1 + 2^2^2 +...+ n^n^n, which has period 100.
%C A229784 Sum of A120962 mod 10. - _T. D. Noe_, Sep 30 2013
%H A229784 Ray Chandler, <a href="/A229784/b229784.txt">Table of n, a(n) for n = 0..999</a>
%H A229784 <a href="/index/Rec#order_83">Index entries for linear recurrences with constant coefficients</a>, signature (1, -1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, -1, 1, -1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, -1, 1, -1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, -1, 1, -1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, -1, 1, -1, 1).
%t A229784 Table[Mod[Sum[PowerMod[i, i^i, 10], {i, 1, n}], 10], {n, 200}]
%t A229784 Mod[Accumulate[Table[PowerMod[i, i^i, 10], {i, 100}]], 10] (* _T. D. Noe_, Sep 30 2013 *)
%o A229784 (PARI) a(n)=lift(sum(k=1,n%100,Mod(k,10)^k^k)) \\ _Charles R Greathouse IV_, Dec 27 2013
%o A229784 (Python)
%o A229784 from itertools import count, accumulate, islice
%o A229784 def A229784_gen(): # generator of terms
%o A229784     yield from accumulate((pow(k,k**k,10) for k in count(1)),func=lambda x,y:(x+y)%10)
%o A229784 A229784_list = list(islice(A229784_gen(),40)) # _Chai Wah Wu_, Jun 17 2022
%Y A229784 Cf. A120962, A185353.
%K A229784 nonn,base,easy
%O A229784 0,3
%A A229784 _José María Grau Ribas_, Sep 29 2013
%E A229784 a(0)=0 prepended by _Alois P. Heinz_, Jun 17 2022