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

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A330945 Numbers whose prime indices are not all prime numbers. 15
 2, 4, 6, 7, 8, 10, 12, 13, 14, 16, 18, 19, 20, 21, 22, 23, 24, 26, 28, 29, 30, 32, 34, 35, 36, 37, 38, 39, 40, 42, 43, 44, 46, 47, 48, 49, 50, 52, 53, 54, 56, 57, 58, 60, 61, 62, 63, 64, 65, 66, 68, 69, 70, 71, 72, 73, 74, 76, 77, 78, 79, 80, 82, 84, 86, 87 (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. LINKS EXAMPLE The sequence of terms together with their prime indices of prime indices begins:    2: {{}}    4: {{},{}}    6: {{},{1}}    7: {{1,1}}    8: {{},{},{}}   10: {{},{2}}   12: {{},{},{1}}   13: {{1,2}}   14: {{},{1,1}}   16: {{},{},{},{}}   18: {{},{1},{1}}   19: {{1,1,1}}   20: {{},{},{2}}   21: {{1},{1,1}}   22: {{},{3}}   23: {{2,2}}   24: {{},{},{},{1}}   26: {{},{1,2}}   28: {{},{},{1,1}}   29: {{1,3}} MATHEMATICA Select[Range[100], !And@@PrimeQ/@PrimePi/@First/@If[#==1, {}, FactorInteger[#]]&] CROSSREFS Complement of A076610 (products of primes of prime index). Numbers n such that A330944(n) > 0. The restriction to odd terms is A330946. The restriction to nonprimes is A330948. 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 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, A320633, A330943, A330947, A330949. Sequence in context: A080645 A024413 A153347 * A153167 A227187 A047237 Adjacent sequences:  A330942 A330943 A330944 * A330946 A330947 A330948 KEYWORD nonn AUTHOR Gus Wiseman, Jan 13 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.

Last modified May 18 13:04 EDT 2021. Contains 343995 sequences. (Running on oeis4.)