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A271410
LCM of exponents in binary expansion of 2n.
11
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, 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, 30, 30, 30, 30, 60, 60, 60, 60, 60, 60, 60, 60, 7, 7, 14, 14, 21, 21, 42
OFFSET
0,3
EXAMPLE
a(2) = lcm(2) = 2 because 2*2 = 2^2;
a(3) = lcm(1, 2) = 2 because 2*3 = 2^1 + 2^2;
a(7) = lcm(1, 2, 3) = 6 because 2*7 = 2^3 + 2^2 + 2^1.
MATHEMATICA
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 *)
PROG
(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
(PARI) a(n)=lcm(Vec(select(x->x, Vecrev(binary(n)), 1))) \\ Charles R Greathouse IV, Apr 12 2016
(Python)
from math import lcm
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
CROSSREFS
KEYWORD
nonn,base,look
AUTHOR
Peter Kagey, Apr 11 2016
STATUS
approved