login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A330949 Odd nonprime numbers whose prime indices are not all prime numbers. 5
21, 35, 39, 49, 57, 63, 65, 69, 77, 87, 91, 95, 105, 111, 115, 117, 119, 129, 133, 141, 143, 145, 147, 159, 161, 169, 171, 175, 183, 185, 189, 195, 203, 207, 209, 213, 215, 217, 219, 221, 231, 235, 237, 245, 247, 253, 259, 261, 265, 267, 273, 285, 287, 291 (list; graph; refs; listen; history; text; internal format)
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.

Also MM-numbers of multiset partitions with at least two parts, not all of which are singletons (see example).

LINKS

Table of n, a(n) for n=1..54.

EXAMPLE

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

   21: {{1},{1,1}}

   35: {{2},{1,1}}

   39: {{1},{1,2}}

   49: {{1,1},{1,1}}

   57: {{1},{1,1,1}}

   63: {{1},{1},{1,1}}

   65: {{2},{1,2}}

   69: {{1},{2,2}}

   77: {{1,1},{3}}

   87: {{1},{1,3}}

   91: {{1,1},{1,2}}

   95: {{2},{1,1,1}}

  105: {{1},{2},{1,1}}

  111: {{1},{1,1,2}}

  115: {{2},{2,2}}

  117: {{1},{1},{1,2}}

  119: {{1,1},{4}}

  129: {{1},{1,4}}

  133: {{1,1},{1,1,1}}

  141: {{1},{2,3}}

MATHEMATICA

Select[Range[1, 100, 2], !PrimeQ[#]&&!And@@PrimeQ/@PrimePi/@First/@If[#==1, {}, FactorInteger[#]]&]

CROSSREFS

Complement of A106092 in A330945.

Including even numbers gives A330948.

Including primes gives A330946.

The number of prime prime indices is given by A257994.

The number of nonprime prime indices is given by A330944.

Primes of prime index are A006450.

Primes of nonprime index are A007821.

Products of primes of prime index are A076610.

Products of primes of nonprime index are A320628.

The set S of numbers whose prime indices do not all belong to S is A324694.

Cf. A000040, A000720, A001222, A018252, A056239, A112798, A302242, A320629, A320633, A330943, A330947.

Sequence in context: A008946 A095738 A216467 * A248020 A290435 A138227

Adjacent sequences:  A330946 A330947 A330948 * A330950 A330951 A330952

KEYWORD

nonn

AUTHOR

Gus Wiseman, Jan 14 2020

STATUS

approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified June 5 03:12 EDT 2020. Contains 334828 sequences. (Running on oeis4.)