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Revision History for A359891

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Members of A026424 (numbers with an odd number of prime factors) whose prime indices have the same mean as median.
(history; published version)
#6 by Michael De Vlieger at Mon Jan 23 09:10:56 EST 2023
STATUS

proposed

approved

#5 by Gus Wiseman at Mon Jan 23 05:07:57 EST 2023
STATUS

editing

proposed

#4 by Gus Wiseman at Mon Jan 23 05:07:49 EST 2023
#3 by Gus Wiseman at Mon Jan 23 01:21:45 EST 2023
NAME

Numbers Members of A026424 (numbers with an odd bigomega number of prime factors) whose prime indices have the same mean as median.

CROSSREFS

A088529/A088530 gives mean of prime signature A124010.

Cf. A135342 subs_ne_dstnct_means, A316313 meansack, A327473, A327476 h_ptns_wo_mean, A327478 bpe_w_mean, A348551 h_nonint_mean, A359894, A359897 strptns_mean_eq_medn, A359898 strptns_mean_neq_medn, A359899 strnptns_oddlen_mean_eq_medn, A359900 strptns_oddlen_mean_neq_medn, A359903 prix_prisig_eq_mean, A359904 prifacs_prisig_eq_mean, A359905 prix_and_prisig_int_mean, A359906 ptns_int_mean_int_medn, A359909 facs_mean_eq_medn, A359910 facs_oddlen_mean_eq_medn, A359912 prix_nonint_medn, A360006 prix_medn_mins, A360007 prix_medn_sortmins, A360008 prix_mean_sortmins, A360009 prix_int_mean_int_medn.

Cf. ~`A135342, A327473, `A327476, ~`A348551, A359894, `A359897, A359899, `A359900, ~`A359909, A359910, `A359912, `A360006, A360007, `~A360008, A360009.

#2 by Gus Wiseman at Sun Jan 22 09:41:42 EST 2023
NAME

allocated for Gus WisemanNumbers with odd bigomega whose prime indices have the same mean as median.

DATA

2, 3, 5, 7, 8, 11, 13, 17, 19, 23, 27, 29, 30, 31, 32, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 105, 107, 109, 110, 113, 125, 127, 128, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233

OFFSET

1,1

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.

The median of a multiset is either the middle part (for odd length), or the average of the two middle parts (for even length).

FORMULA

Intersection of A026424 and A359889.

EXAMPLE

The terms together with their prime indices begin:

2: {1}

3: {2}

5: {3}

7: {4}

8: {1,1,1}

11: {5}

13: {6}

17: {7}

19: {8}

23: {9}

27: {2,2,2}

29: {10}

30: {1,2,3}

31: {11}

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

For example, the prime indices of 180 are {1,1,2,2,3}, with mean 9/5 and median 2, so 180 is not in the sequence.

MATHEMATICA

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

Select[Range[100], OddQ[PrimeOmega[#]]&&Mean[prix[#]]==Median[prix[#]]&]

CROSSREFS

A subset of A026424 = numbers with odd bigomega.

The LHS (mean of prime indices) is A326567/A326568.

This is the odd-length case of A359889, complement A359890.

The complement is A359892.

These partitions are counted by A359895, any-length A240219.

The RHS (median of prime indices) is A360005/2.

A058398 counts partitions by mean, see also A008284, A327482.

A088529/A088530 gives mean of prime signature A124010.

A112798 lists prime indices, length A001222, sum A056239.

A316413 lists numbers whose prime indices have integer mean.

A359893 and A359901 count partitions by median, odd-length A359902.

A359908 lists numbers whose prime indices have integer median.

Cf. A135342 subs_ne_dstnct_means, A316313 meansack, A327473, A327476 h_ptns_wo_mean, A327478 bpe_w_mean, A348551 h_nonint_mean, A359894, A359897 strptns_mean_eq_medn, A359898 strptns_mean_neq_medn, A359899 strnptns_oddlen_mean_eq_medn, A359900 strptns_oddlen_mean_neq_medn, A359903 prix_prisig_eq_mean, A359904 prifacs_prisig_eq_mean, A359905 prix_and_prisig_int_mean, A359906 ptns_int_mean_int_medn, A359909 facs_mean_eq_medn, A359910 facs_oddlen_mean_eq_medn, A359912 prix_nonint_medn, A360006 prix_medn_mins, A360007 prix_medn_sortmins, A360008 prix_mean_sortmins, A360009 prix_int_mean_int_medn.

KEYWORD

allocated

nonn

AUTHOR

Gus Wiseman, Jan 22 2023

STATUS

approved

editing

#1 by Gus Wiseman at Tue Jan 17 23:19:16 EST 2023
NAME

allocated for Gus Wiseman

KEYWORD

allocated

STATUS

approved