This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A320630 Products of primes of nonprime squarefree index. 3
 2, 4, 8, 13, 16, 26, 29, 32, 43, 47, 52, 58, 64, 73, 79, 86, 94, 101, 104, 113, 116, 128, 137, 139, 146, 149, 158, 163, 167, 169, 172, 181, 188, 199, 202, 208, 226, 232, 233, 256, 257, 269, 271, 274, 278, 292, 293, 298, 313, 316, 317, 326, 334, 338, 344, 347 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS The index of a prime number n is the number m such that n is the m-th prime. LINKS EXAMPLE The sequence of terms begins:     2 = prime(1)     4 = prime(1)^2     8 = prime(1)^3    13 = prime(6)    16 = prime(1)^4    26 = prime(1)*prime(6)    29 = prime(10)    32 = prime(1)^5    43 = prime(14)    47 = prime(15)    52 = prime(1)^2*prime(6)    58 = prime(1)*prime(10)    64 = prime(1)^6    73 = prime(21)    79 = prime(22)    86 = prime(1)*prime(14)    94 = prime(1)*prime(15)   101 = prime(26)   104 = prime(1)^3*prime(6)   113 = prime(30)   116 = prime(1)^2*prime(10)   128 = prime(1)^7 MATHEMATICA Select[Range[100], With[{f=PrimePi/@First/@FactorInteger[#]}, And[And@@SquareFreeQ/@f, And@@Not/@PrimeQ/@f]]&] CROSSREFS Cf. A000040, A006450, A007821, A018252, A056239, A076610, A112798, A302242, A302478, A320628, A320629, A320631, A320633. Sequence in context: A133802 A076202 A268713 * A224399 A114398 A107326 Adjacent sequences:  A320627 A320628 A320629 * A320631 A320632 A320633 KEYWORD nonn AUTHOR Gus Wiseman, Oct 18 2018 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 September 16 08:53 EDT 2019. Contains 327092 sequences. (Running on oeis4.)