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A161538 Numbers n such that composite (n) + n is a prime, where composite (n) denotes the n-th composite number. 1
1, 3, 4, 8, 11, 27, 29, 40, 44, 45, 47, 57, 58, 66, 69, 71, 83, 84, 90, 100, 103, 108, 111, 116, 117, 127, 133, 135, 136, 144, 147, 151, 153, 156, 160, 163, 176, 179, 197, 201, 211, 214, 216, 221, 239, 242, 251, 252, 255, 260, 263, 269, 272, 274, 275, 280, 287 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

8 is in the list because composite(8) + 8 = 15 + 8 = 23 is prime.

27 is in the list because composite(27) + 27 = 40 + 27 = 67 is prime.

LINKS

Table of n, a(n) for n=1..57.

MATHEMATICA

nn=400; With[{cnos=Rest[Complement[Range[nn], Prime[Range[PrimePi[nn]]]]]}, Transpose[Select[Thread[{cnos, Range[Length[cnos]]}], PrimeQ[Total[#]]&]][[2]]] (* Harvey P. Dale, Mar 24 2011 *)

CROSSREFS

Cf. A002808.

Complement of A161539.

Sequence in context: A126873 A263768 A050316 * A319980 A170885 A080646

Adjacent sequences:  A161535 A161536 A161537 * A161539 A161540 A161541

KEYWORD

nonn

AUTHOR

Claudio Meller, Jun 13 2009

STATUS

approved

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Last modified July 29 13:28 EDT 2021. Contains 346346 sequences. (Running on oeis4.)