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A171575 n-th noncomposite number plus n-th even nonprime number. 0
1, 6, 9, 13, 17, 23, 27, 33, 37, 43, 51, 55, 63, 69, 73, 79, 87, 95, 99, 107, 113, 117, 125, 131, 139, 149, 155, 159, 165, 169, 175, 191, 197, 205, 209, 221, 225, 233, 241, 247, 255, 263, 267, 279, 283, 289, 293, 307, 321, 327, 331, 337, 345, 349, 361, 369, 377 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

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

FORMULA

a(n) = A008578(n) + A163300(n).

EXAMPLE

a(1) = 1 + 0 = 1, a(2) = 2 + 4 = 6, a(3) = 3 + 6 = 9.

MATHEMATICA

Module[{nc=Select[Range[300], !CompositeQ[#]&], len}, len=Length[nc]; Join[ {1}, Rest[Total/@Thread[{nc, Range[2, 2len, 2]}]]]] (* Harvey P. Dale, Mar 08 2018 *)

CROSSREFS

Cf. A008578(the noncomposite numbers), A163300(the even nonprime numbers).

Sequence in context: A236763 A030499 A181428 * A186524 A315963 A315964

Adjacent sequences:  A171572 A171573 A171574 * A171576 A171577 A171578

KEYWORD

nonn

AUTHOR

Juri-Stepan Gerasimov, Dec 12 2009

EXTENSIONS

Entries checked by R. J. Mathar, May 23 2010

STATUS

approved

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Last modified January 19 18:13 EST 2020. Contains 331051 sequences. (Running on oeis4.)