A127118 a(n) = n-th prime * n-th nonprime.

2, 12, 30, 56, 99, 130, 204, 266, 345, 464, 558, 740, 861, 946, 1128, 1325, 1534, 1647, 1876, 2130, 2336, 2607, 2822, 3115, 3492, 3838, 4017, 4280, 4578, 4972, 5715, 6026, 6576, 6811, 7450, 7701, 8164, 8802, 9185, 9688, 10203, 10498, 11460, 11966, 12411

Offset

1,1

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Formula

a(n) = A000040(n) * A018252(n).

Mathematica

Module[{nn=100, prs, non, len}, prs=Prime[Range[nn]]; non=Complement[ Range[ nn], prs]; len=Min[Length[prs], Length[non]]; Times@@#&/@ Thread[ {Take[ prs, len], Take[non, len]}]] (* Harvey P. Dale, Dec 29 2012 *)

Prog

(Haskell)
a127118 n = a000040 n * a018252 n  -- Reinhard Zumkeller, Apr 30 2014
(Python)
from sympy import prime, composite
def A127118(n):
    return 2 if n == 1 else prime(n)*composite(n-1) # Chai Wah Wu, Dec 27 2018

Crossrefs

Cf. A000040, A018252, A002808.

Cf. A014237, A064799, A067563.

Sequence in context: A002939 A118239 A249055 * A259127 A296257 A301774

Adjacent sequences: A127115 A127116 A127117 * A127119 A127120 A127121

Keyword

nonn,easy

Author

Neven Juric (neven.juric(AT)apis-it.hr), Mar 21 2007

Status

approved