A271410 - OEIS

%I #60 Jun 12 2023 17:08:23

%S 1,1,2,2,3,3,6,6,4,4,4,4,12,12,12,12,5,5,10,10,15,15,30,30,20,20,20,

%T 20,60,60,60,60,6,6,6,6,6,6,6,6,12,12,12,12,12,12,12,12,30,30,30,30,

%U 30,30,30,30,60,60,60,60,60,60,60,60,7,7,14,14,21,21,42

%N LCM of exponents in binary expansion of 2n.

%H Peter Kagey, <a href="/A271410/b271410.txt">Table of n, a(n) for n = 0..10000</a>

%e a(2) = lcm(2) = 2 because 2*2 = 2^2;

%e a(3) = lcm(1, 2) = 2 because 2*3 = 2^1 + 2^2;

%e a(7) = lcm(1, 2, 3) = 6 because 2*7 = 2^3 + 2^2 + 2^1.

%t lcm[n_]:=Module[{idn2=IntegerDigits[n,2]},LCM@@Pick[Reverse[Range[ Length[ idn2]]], idn2,1]]; Join[{1},Array[lcm,100]] (* _Harvey P. Dale_, Jan 24 2019 *)

%o (PARI) a(n) = my(ve = select(x->x==1, Vecrev(binary(2*n)), 1)); lcm(vector(#ve, k, ve[k]-1)); \\ _Michel Marcus_, Apr 12 2016

%o (PARI) a(n)=lcm(Vec(select(x->x, Vecrev(binary(n)), 1))) \\ _Charles R Greathouse IV_, Apr 12 2016

%o (Python)

%o from math import lcm

%o def A271410(n): return lcm(*(i for i, b in enumerate(bin(n)[:1:-1],1) if b == '1')) # _Chai Wah Wu_, Dec 12 2022

%Y Cf. A029931, A064894, A073642, A096111, A116417.

%K nonn,base,look

%O 0,3

%A _Peter Kagey_, Apr 11 2016