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

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, 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, 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

Offset: 1

Author

Ralf Stephan, Oct 23 2004

Keywords

• nonn
• base
• easy

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000265, A010879.

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

Programs

Maple

f:= n -> n/2^padic:-ordp(n,2) mod 10:
map(f, [$1..200]); # Robert Israel, Aug 10 2018

Mathematica

Mod[Table[Max[Select[Divisors[n],OddQ]],{n,110}],10] (* Harvey P. Dale, Jun 22 2017 *)
a[n_] := Mod[n / 2^IntegerExponent[n, 2], 10]; Array[a, 100] (* Amiram Eldar, Aug 29 2024 *)

PARI

a(n)=(n>>valuation(n,2))%10 \\ Charles R Greathouse IV, Dec 28 2012

Formula

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

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

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