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A337645 a(1)=2; thereafter, a(n) = smallest number with at least two different prime factors that is missing from A336957 after A336957(n) has been found. 4
2, 6, 10, 10, 10, 10, 10, 10, 10, 18, 20, 20, 20, 20, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 36, 36, 36, 36, 44, 44, 44, 44, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 54 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The initial 2 is an exception. For n>2, A336957(n) is required to have at least two different prime factors.

It is conjectured that every number with at least two different prime factors will eventually appear in A336957.

LINKS

N. J. A. Sloane, Table of n, a(n) for n = 1..20000

EXAMPLE

A336957 begins 1, 2, 6, 15, 35, 14, with A336957(6)=14. At that point 10 is the smallest legal candidate that has not yet appeared, so a(6) = 10.

CROSSREFS

Cf. A336957, A338052, A338058.

Sequence in context: A122882 A136700 A054645 * A225271 A050425 A030405

Adjacent sequences:  A337642 A337643 A337644 * A337646 A337647 A337648

KEYWORD

nonn

AUTHOR

Scott R. Shannon and N. J. A. Sloane, Sep 25 2020; corrected Oct 11 2020

STATUS

approved

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Last modified June 28 16:56 EDT 2022. Contains 354907 sequences. (Running on oeis4.)