A297850 - OEIS

A297850

Least common prime factor of the members of n-th amicable pair, or 0 if the two members of the pair are coprime.

2, 2, 2, 2, 2, 2, 3, 2, 2, 2, 3, 3, 2, 3, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 2, 2, 2, 2, 2, 2, 2, 3, 2, 2, 3, 2, 2, 2, 2, 3, 2, 3, 2, 3, 2, 2, 2, 2, 2, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 2, 2, 2, 2, 2, 3, 2, 2, 2, 3, 2, 2, 3, 2, 2

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OFFSET

1,1

COMMENTS

The question whether a(n) = 0 for any n is an open problem.

This is different from A171092 (cf. Chernykh link).

If a(n) = 0, then A001221(A259180(2*n-1)*A259180(2*n)) > 21 (cf. Hagis, 1975).

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000

Sergei Chernykh, Amicable pairs news

Peter Hagis, Jr., On the Number of Prime Factors of a Pair of Relatively Prime Amicable Numbers, Mathematics Magazine, Vol. 48, No. 5 (1975), pp. 263-266.

Wikipedia, Amicable numbers.