A340606 - OEIS

A340606

Numbers whose prime indices (A112798) are all divisors of the number of prime factors (A001222).

1, 2, 4, 6, 8, 9, 16, 20, 24, 32, 36, 50, 54, 56, 64, 81, 84, 96, 125, 126, 128, 144, 160, 176, 189, 196, 216, 240, 256, 294, 324, 360, 384, 400, 416, 441, 486, 512, 540, 576, 600, 624, 686, 729, 810, 864, 896, 900, 936, 968, 1000, 1024, 1029, 1040, 1088, 1215

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OFFSET

1,2

COMMENTS

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..56.

EXAMPLE

The sequence of terms together with their prime indices begins:

1: {}

2: {1}

4: {1,1}

6: {1,2}

8: {1,1,1}

9: {2,2}

16: {1,1,1,1}

20: {1,1,3}

24: {1,1,1,2}

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

36: {1,1,2,2}

50: {1,3,3}

54: {1,2,2,2}

56: {1,1,1,4}

64: {1,1,1,1,1,1}

81: {2,2,2,2}

84: {1,1,2,4}

96: {1,1,1,1,1,2}

MATHEMATICA

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

Select[Range[100], And@@IntegerQ/@(PrimeOmega[#]/primeMS[#])&]

CROSSREFS

Note: Heinz numbers are given in parentheses below.

The reciprocal version is A143773 (A316428).

These partitions are counted by A340693.

A120383 lists numbers divisible by all of their prime indices.

A324850 lists numbers divisible by the product of their prime indices.

A003963 multiplies together the prime indices of n.

A018818 counts partitions of n into divisors of n (A326841).

A047993 counts balanced partitions (A106529).

A067538 counts partitions of n whose length divides n (A316413).

A056239 adds up the prime indices of n.

A061395 selects the maximum prime index.

A067538 counts partitions of n whose maximum divides n (A326836).

A072233 counts partitions by sum and length.

A112798 lists the prime indices of each positive integer.

A168659 = partitions whose length is divisible by their maximum (A340609).

A168659 = partitions whose maximum is divisible by their length (A340610).

A289509 lists numbers with relatively prime prime indices.

A326842 = partitions of n whose length and parts all divide n (A326847).

A326843 = partitions of n whose length and maximum both divide n (A326837).

A340852 have a factorization with factors dividing length.

Cf. A000720, A001222, A006141, A067539, A200750, A298423, A324925, A326149/A326155, A340608, A340827.

Sequence in context: A080223 A156759 A340609 * A276138 A114973 A004522

Adjacent sequences: A340603 A340604 A340605 * A340607 A340608 A340609

KEYWORD

nonn

AUTHOR

Gus Wiseman, Jan 24 2021

STATUS

approved