login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A328603 Numbers whose prime indices have no consecutive divisible parts, meaning no prime index is a divisor of the next-smallest prime index, counted with multiplicity. 9

%I #7 Oct 29 2019 21:08:42

%S 1,2,3,5,7,11,13,15,17,19,23,29,31,33,35,37,41,43,47,51,53,55,59,61,

%T 67,69,71,73,77,79,83,85,89,91,93,95,97,101,103,105,107,109,113,119,

%U 123,127,131,137,139,141,143,145,149,151,155,157,161,163,165,167

%N Numbers whose prime indices have no consecutive divisible parts, meaning no prime index is a divisor of the next-smallest prime index, counted with multiplicity.

%C First differs from A304713 in having 105, with prime indices {2, 3, 4}.

%C 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.

%F Intersection of A005117 and A328674.

%e The sequence of terms together with their prime indices begins:

%e 1: {}

%e 2: {1}

%e 3: {2}

%e 5: {3}

%e 7: {4}

%e 11: {5}

%e 13: {6}

%e 15: {2,3}

%e 17: {7}

%e 19: {8}

%e 23: {9}

%e 29: {10}

%e 31: {11}

%e 33: {2,5}

%e 35: {3,4}

%e 37: {12}

%e 41: {13}

%e 43: {14}

%e 47: {15}

%e 51: {2,7}

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

%t Select[Range[100],!MatchQ[primeMS[#],{___,x_,y_,___}/;Divisible[y,x]]&]

%Y A subset of A005117.

%Y These are the Heinz numbers of the partitions counted by A328171.

%Y The non-strict version is A328674 (Heinz numbers for A328675).

%Y The version for relatively prime instead of indivisible is A328335.

%Y Compositions without consecutive divisibilities are A328460.

%Y Numbers whose binary indices lack consecutive divisibilities are A328593.

%Y The version with all pairs indivisible is A304713.

%Y Cf. A056239, A112798, A316476, A318726, A318729, A326704, A328336, A328598, A328599.

%K nonn

%O 1,2

%A _Gus Wiseman_, Oct 26 2019

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified August 3 10:11 EDT 2024. Contains 374885 sequences. (Running on oeis4.)