cp's OEIS Frontend

A099551 Odd part of n modulo 10. Final digit of A000265(n).

%I A099551 #19 Aug 29 2024 09:15:53
%S A099551 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 A099551 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 A099551 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 A099551 Odd part of n modulo 10. Final digit of A000265(n).
%H A099551 Robert Israel, <a href="/A099551/b099551.txt">Table of n, a(n) for n = 1..10000</a>
%F A099551 a(n) = A010879(A000265(n)).
%F A099551 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 A099551 Asymptotic mean: Limit_{m->oo} (1/m) * Sum_{k=1..m} a(k) = 5. - _Amiram Eldar_, Aug 29 2024
%p A099551 f:= n -> n/2^padic:-ordp(n,2) mod 10:
%p A099551 map(f, [$1..200]); # _Robert Israel_, Aug 10 2018
%t A099551 Mod[Table[Max[Select[Divisors[n],OddQ]],{n,110}],10] (* _Harvey P. Dale_, Jun 22 2017 *)
%t A099551 a[n_] := Mod[n / 2^IntegerExponent[n, 2], 10]; Array[a, 100] (* _Amiram Eldar_, Aug 29 2024 *)
%o A099551 (PARI) a(n)=(n>>valuation(n,2))%10 \\ _Charles R Greathouse IV_, Dec 28 2012
%Y A099551 Cf. A000265, A010879.
%Y A099551 Cf. A099544, A099545, A099546, A099547, A099548, A099549, A099550.
%K A099551 nonn,base,easy
%O A099551 1,3
%A A099551 _Ralf Stephan_, Oct 23 2004