A324705 - OEIS

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A324705

Lexicographically earliest sequence containing 1 and all composite numbers divisible by prime(m) for some m already in the sequence.

1, 4, 6, 8, 10, 12, 14, 16, 18, 20, 21, 22, 24, 26, 28, 30, 32, 34, 35, 36, 38, 39, 40, 42, 44, 46, 48, 49, 50, 52, 54, 56, 57, 58, 60, 62, 63, 64, 65, 66, 68, 70, 72, 74, 76, 77, 78, 80, 82, 84, 86, 87, 88, 90, 91, 92, 94, 95, 96, 98, 100, 102, 104, 105, 106

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

COMMENTS

A self-describing sequence, similar to A304360.

A prime index of n is a number m such that prime(m) divides n. The multiset of prime indices of n is row n of A112798.

LINKS

Table of n, a(n) for n=1..65.

EXAMPLE

The sequence of terms together with their prime indices begins:

1: {}

4: {1,1}

6: {1,2}

8: {1,1,1}

10: {1,3}

12: {1,1,2}

14: {1,4}

16: {1,1,1,1}

18: {1,2,2}

20: {1,1,3}

21: {2,4}

22: {1,5}

24: {1,1,1,2}

26: {1,6}

28: {1,1,4}

30: {1,2,3}

32: {1,1,1,1,1}

34: {1,7}

35: {3,4}

36: {1,1,2,2}

MATHEMATICA

aQ[n_]:=Switch[n, 1, True, _?PrimeQ, False, _, !And@@Cases[FactorInteger[n], {p_, k_}:>!aQ[PrimePi[p]]]];

Select[Range[200], aQ]

CROSSREFS

Complement of A324697.

Cf. A000002, A000720, A001222, A001462, A007097, A055396, A061395, A079000, A079254, A109298, A112798, A276625, A277098, A304360.

Cf. A324694, A324695, A324696, A324698, A324699, A324700, A324701, A324702, A324703, A324704.

Sequence in context: A185604 A054023 A330948 * A032583 A175074 A063127

Adjacent sequences: A324702 A324703 A324704 * A324706 A324707 A324708

KEYWORD

nonn

AUTHOR

Gus Wiseman, Mar 11 2019

STATUS

approved