A309765 a(n) is the least k>=1 such that k*(k+1) is divisible by A003418(n).

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

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