cp's OEIS Frontend

A271410 LCM of exponents in binary expansion of 2n.

%I A271410 #60 Jun 12 2023 17:08:23
%S A271410 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 A271410 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 A271410 30,30,30,30,60,60,60,60,60,60,60,60,7,7,14,14,21,21,42
%N A271410 LCM of exponents in binary expansion of 2n.
%H A271410 Peter Kagey, <a href="/A271410/b271410.txt">Table of n, a(n) for n = 0..10000</a>
%e A271410 a(2) = lcm(2) = 2 because 2*2 = 2^2;
%e A271410 a(3) = lcm(1, 2) = 2 because 2*3 = 2^1 + 2^2;
%e A271410 a(7) = lcm(1, 2, 3) = 6 because 2*7 = 2^3 + 2^2 + 2^1.
%t A271410 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 A271410 (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 A271410 (PARI) a(n)=lcm(Vec(select(x->x, Vecrev(binary(n)), 1))) \\ _Charles R Greathouse IV_, Apr 12 2016
%o A271410 (Python)
%o A271410 from math import lcm
%o A271410 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 A271410 Cf. A029931, A064894, A073642, A096111, A116417.
%K A271410 nonn,base,look
%O A271410 0,3
%A A271410 _Peter Kagey_, Apr 11 2016