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!)
A332831 Numbers whose unsorted prime signature is neither weakly increasing nor weakly decreasing. 16

%I #9 Mar 02 2020 18:54:45

%S 90,126,198,234,270,300,306,342,350,378,414,522,525,540,550,558,588,

%T 594,600,630,650,666,702,738,756,774,810,825,846,850,918,950,954,975,

%U 980,990,1026,1050,1062,1078,1098,1134,1150,1170,1176,1188,1200,1206,1242

%N Numbers whose unsorted prime signature is neither weakly increasing nor weakly decreasing.

%C A number's prime signature (row n of A124010) is the sequence of positive exponents in its prime factorization.

%F Intersection of A071365 and A112769.

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

%e 90: {1,2,2,3}

%e 126: {1,2,2,4}

%e 198: {1,2,2,5}

%e 234: {1,2,2,6}

%e 270: {1,2,2,2,3}

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

%e 306: {1,2,2,7}

%e 342: {1,2,2,8}

%e 350: {1,3,3,4}

%e 378: {1,2,2,2,4}

%e 414: {1,2,2,9}

%e 522: {1,2,2,10}

%e 525: {2,3,3,4}

%e 540: {1,1,2,2,2,3}

%e 550: {1,3,3,5}

%e 558: {1,2,2,11}

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

%e 594: {1,2,2,2,5}

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

%e 630: {1,2,2,3,4}

%e For example, the prime signature of 540 is (2,3,1), so 540 is in the sequence.

%t Select[Range[1000],!Or[LessEqual@@Last/@FactorInteger[#],GreaterEqual@@Last/@FactorInteger[#]]&]

%Y The version for run-lengths of partitions is A332641.

%Y The version for run-lengths of compositions is A332833.

%Y The version for compositions is A332834.

%Y Prime signature is A124010.

%Y Unimodal compositions are A001523.

%Y Partitions with weakly increasing run-lengths are A100883.

%Y Partitions with weakly increasing or decreasing run-lengths are A332745.

%Y Compositions with weakly increasing or decreasing run-lengths are A332835.

%Y Compositions with weakly increasing run-lengths are A332836.

%Y Cf. A100882, A115981, A328509, A329398, A332281, A332640, A332643, A332746, A332836, A332870.

%K nonn

%O 1,1

%A _Gus Wiseman_, Mar 02 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 June 21 02:50 EDT 2024. Contains 373535 sequences. (Running on oeis4.)