A099551 - OEIS

%I #19 Aug 29 2024 09:15:53

%S 1,1,3,1,5,3,7,1,9,5,1,3,3,7,5,1,7,9,9,5,1,1,3,3,5,3,7,7,9,5,1,1,3,7,

%T 5,9,7,9,9,5,1,1,3,1,5,3,7,3,9,5,1,3,3,7,5,7,7,9,9,5,1,1,3,1,5,3,7,7,

%U 9,5,1,9,3,7,5,9,7,9,9,5,1,1,3,1,5,3,7,1,9,5,1,3,3,7,5,3,7,9,9,5,1,1

%N Odd part of n modulo 10. Final digit of A000265(n).

%H Robert Israel, <a href="/A099551/b099551.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) = A010879(A000265(n)).

%F G.f. g(x) satisfies: g(x) = g(x^2) + (x + 3*x^3 + 5*x^5 + 7*x^7 + 9*x^9)/(1-x^10). - _Robert Israel_, Aug 10 2018

%F Asymptotic mean: Limit_{m->oo} (1/m) * Sum_{k=1..m} a(k) = 5. - _Amiram Eldar_, Aug 29 2024

%p f:= n -> n/2^padic:-ordp(n,2) mod 10:

%p map(f, [$1..200]); # _Robert Israel_, Aug 10 2018

%t Mod[Table[Max[Select[Divisors[n],OddQ]],{n,110}],10] (* _Harvey P. Dale_, Jun 22 2017 *)

%t a[n_] := Mod[n / 2^IntegerExponent[n, 2], 10]; Array[a, 100] (* _Amiram Eldar_, Aug 29 2024 *)

%o (PARI) a(n)=(n>>valuation(n,2))%10 \\ _Charles R Greathouse IV_, Dec 28 2012

%Y Cf. A000265, A010879.

%Y Cf. A099544, A099545, A099546, A099547, A099548, A099549, A099550.

%K nonn,base,easy

%O 1,3

%A _Ralf Stephan_, Oct 23 2004