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!)
A332282 Numbers whose unsorted prime signature is not unimodal. 37

%I #4 Feb 21 2020 12:30:59

%S 300,588,600,980,1176,1200,1452,1500,1960,2028,2100,2205,2352,2400,

%T 2420,2904,2940,3000,3300,3380,3388,3468,3900,3920,4056,4116,4200,

%U 4332,4410,4704,4732,4800,4840,5100,5445,5700,5780,5808,5880,6000,6348,6468,6600,6615

%N Numbers whose unsorted prime signature is not unimodal.

%C The unsorted prime signature of a positive integer (row n of A124010) is the sequence of exponents it is prime factorization.

%C A sequence of positive integers is unimodal if it is the concatenation of a weakly increasing and a weakly decreasing sequence.

%C Also Heinz numbers of integer partitions with non-unimodal run-lengths. The Heinz number of an integer partition (y_1,...,y_k) is prime(y_1)*...*prime(y_k).

%H MathWorld, <a href="http://mathworld.wolfram.com/UnimodalSequence.html">Unimodal Sequence</a>

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

%e 300: {1,1,2,3,3}

%e 588: {1,1,2,4,4}

%e 600: {1,1,1,2,3,3}

%e 980: {1,1,3,4,4}

%e 1176: {1,1,1,2,4,4}

%e 1200: {1,1,1,1,2,3,3}

%e 1452: {1,1,2,5,5}

%e 1500: {1,1,2,3,3,3}

%e 1960: {1,1,1,3,4,4}

%e 2028: {1,1,2,6,6}

%e 2100: {1,1,2,3,3,4}

%e 2205: {2,2,3,4,4}

%e 2352: {1,1,1,1,2,4,4}

%e 2400: {1,1,1,1,1,2,3,3}

%e 2420: {1,1,3,5,5}

%e 2904: {1,1,1,2,5,5}

%e 2940: {1,1,2,3,4,4}

%e 3000: {1,1,1,2,3,3,3}

%e 3300: {1,1,2,3,3,5}

%e 3380: {1,1,3,6,6}

%t unimodQ[q_]:=Or[Length[q]==1,If[q[[1]]<=q[[2]],unimodQ[Rest[q]],OrderedQ[Reverse[q]]]];

%t Select[Range[1000],!unimodQ[Last/@FactorInteger[#]]&]

%Y The opposite version is A332642.

%Y These are the Heinz numbers of the partitions counted by A332281.

%Y Non-unimodal permutations are A059204.

%Y Non-unimodal compositions are A115981.

%Y Non-unimodal normal sequences are A328509.

%Y Cf. A001523, A007052, A056239, A112798, A124010, A227038, A332280, A332284, A332286, A332639, A332643, A332671.

%K nonn

%O 1,1

%A _Gus Wiseman_, Feb 19 2020

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 April 23 09:22 EDT 2024. Contains 371905 sequences. (Running on oeis4.)