A175077 - OEIS

%I #19 Jun 15 2023 04:37:20

%S 1,2,1,1,2,1,2,1,2,1,1,1,2,1,2,1,1,1,2,1,2,1,1,1,2,1,1,2,1,1,2,1,2,1,

%T 1,2,1,1,2,1,1,1,2,1,2,1,1,1,2,1,1,2,1,1,2,1,1,2,1,1,2,1,2,1,1,2,1,1,

%U 2,1,1,1,2,1,2,1,1,2,1,1,2,1,1,1,2,1,1,2,1,1,2,1,1,2,1,2,1,1,2,1,1,1,2,1,2,1

%N Final number reached by iterating r -> A049711(r) starting at r = n.

%C See A175071 for starting n that reach 1, and A175072 for starting n that reach 2.

%F a(A175071(k)) = 1; a(A175072(k)) = 2, any k. - _R. J. Mathar_, Feb 19 2010

%F a(n) = A121559(n-1) + 1 for n >= 2. - _Pontus von Brömssen_, Jul 31 2022

%e Iteration procedure for n = 6: 6 mod 5 = 1 = a(6).

%e Iteration procedure for n = 7: 7 mod 5 = 2 = a(7).

%p A151799 := proc(n) prevprime(n) ; end proc:

%p A049711 := proc(n) if n <=2 then n; else n-A151799(n) ; end if; end proc:

%p A175077 := proc(n) local r ; r := n ; while r > 2 do r := A049711(r) ; end do: r ; end proc:

%p seq(A175077(n),n=1..100) ; # _R. J. Mathar_, Feb 19 2010

%t f[n_] := Switch[n, 1, 1, 2, 2, _, n - NextPrime[n, -1]];

%t a[n_] := FixedPoint[f, n];

%t Table[a[n], {n, 1, 100}] (* _Jean-François Alcover_, Jun 13 2023 *)

%Y Cf. A049711, A121559, A151799, A175071, A175072.

%K nonn

%O 1,2

%A _Jaroslav Krizek_, Jan 23 2010

%E More terms from _R. J. Mathar_, Feb 19 2010