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 A309765 a(n) is the least k>=1 such that k*(k+1) is divisible by A003418(n). 1
 1, 1, 2, 3, 15, 15, 20, 104, 224, 224, 440, 440, 2079, 2079, 2079, 2079, 194480, 194480, 1956240, 1956240, 1956240, 1956240, 6113744, 6113744, 19706400, 19706400, 317839599, 317839599, 2183843375, 2183843375, 6081487775, 6081487775, 6081487775, 6081487775, 6081487775, 6081487775 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS Bert Dobbelaere, Table of n, a(n) for n = 1..172 Bert Dobbelaere, Python program EXAMPLE a(3)=2 because A003418(3)=6 divides 2*3 but does not divide 1*2. MAPLE A[1]:= 1: X:=[]: P:=[]: S:= [[]]: for n from 2 to 50 do F:= ifactors(n)[2]; found:= false; for t in F do if member(t[1], P, 'i') then if t[1]^t[2]>X[i] then found:= true; X:= subsop(i=t[1]^t[2], X); fi else found:= true; X:= [op(X), t[1]]; P:= [op(P), t[1]]; S:= map(t -> ([op(t), 0], [op(t), -1]), S); fi; od; if found then A[n]:= min(map(x -> chrem(x, X), S[2..-1])); else A[n]:= A[n-1] fi; od: seq(A[i], i=1..50); CROSSREFS Cf. A003418. Sequence in context: A088030 A101047 A251618 * A238691 A241721 A066491 Adjacent sequences: A309762 A309763 A309764 * A309766 A309767 A309768 KEYWORD nonn AUTHOR J. M. Bergot and Robert Israel, Aug 15 2019 STATUS approved

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Last modified September 7 17:00 EDT 2024. Contains 375749 sequences. (Running on oeis4.)