A320631 Products of odd primes of nonprime squarefree index.

13, 29, 43, 47, 73, 79, 101, 113, 137, 139, 149, 163, 167, 169, 181, 199, 233, 257, 269, 271, 293, 313, 317, 347, 349, 373, 377, 389, 397, 421, 439, 443, 449, 467, 487, 491, 499, 557, 559, 571, 577, 601, 607, 611, 619, 631, 647, 653, 673, 677, 727, 733, 751

Offset

1,1

Links

Table of n, a(n) for n=1..53.

Example

The sequence of terms begins:
   13 = prime(6)
   29 = prime(10)
   43 = prime(14)
   47 = prime(15)
   73 = prime(21)
   79 = prime(22)
  101 = prime(26)
  113 = prime(30)
  137 = prime(33)
  139 = prime(34)
  149 = prime(35)
  163 = prime(38)
  167 = prime(39)
  169 = prime(6)^2
  181 = prime(42)
  199 = prime(46)
  233 = prime(51)
  257 = prime(55)
  269 = prime(57)
  271 = prime(58)
  293 = prime(62)
  313 = prime(65)
  317 = prime(66)
  347 = prime(69)
  349 = prime(70)
  373 = prime(74)
  377 = prime(6)*prime(10)

Mathematica

Select[Range[1, 100, 2], 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, A320630, A320633.

Sequence in context: A339989 A120827 A369863 * A339113 A309356 A322551

Adjacent sequences: A320628 A320629 A320630 * A320632 A320633 A320634

Keyword

nonn

Author

Gus Wiseman, Oct 18 2018

Status

approved