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A302594 Numbers whose prime indices other than 1 are equal prime numbers. 0
1, 2, 3, 4, 5, 6, 8, 9, 10, 11, 12, 16, 17, 18, 20, 22, 24, 25, 27, 31, 32, 34, 36, 40, 41, 44, 48, 50, 54, 59, 62, 64, 67, 68, 72, 80, 81, 82, 83, 88, 96, 100, 108, 109, 118, 121, 124, 125, 127, 128, 134, 136, 144, 157, 160, 162, 164, 166, 176, 179, 191, 192 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

A prime index of n is a number m such that prime(m) divides n.

LINKS

Table of n, a(n) for n=1..62.

EXAMPLE

Entry A302242 describes a correspondence between positive integers and multiset multisystems. In this case it gives the following sequence of set systems.

01: {}

02: {{}}

03: {{1}}

04: {{},{}}

05: {{2}}

06: {{},{1}}

08: {{},{},{}}

09: {{1},{1}}

10: {{},{2}}

11: {{3}}

12: {{},{},{1}}

16: {{},{},{},{}}

17: {{4}}

18: {{},{1},{1}}

20: {{},{},{2}}

22: {{},{3}}

24: {{},{},{},{1}}

MATHEMATICA

primeMS[n_]:=If[n===1, {}, Flatten[Cases[FactorInteger[n], {p_, k_}:>Table[PrimePi[p], {k}]]]];

Select[Range[400], MatchQ[Union[DeleteCases[primeMS[#], 1]], {_?PrimeQ}|{}]&]

CROSSREFS

Cf. A000961, A001222, A003963, A005117, A006450, A007716, A056239, A076610, A275024, A047968, A281113, A295924, A301760, A302242, A302243.

Sequence in context: A325663 A277620 A031143 * A055492 A005459 A039216

Adjacent sequences:  A302591 A302592 A302593 * A302595 A302596 A302597

KEYWORD

nonn

AUTHOR

Gus Wiseman, Apr 10 2018

STATUS

approved

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Last modified September 21 13:20 EDT 2020. Contains 337272 sequences. (Running on oeis4.)