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A162887 Odd nonprimes in an alternating 1-based sum up to some odd nonprime. 0
15, 33, 39, 51, 69, 75, 87, 105, 117, 123, 129, 141, 159, 177, 183, 189, 195, 201, 213, 219, 231, 243, 249, 255, 267, 279, 285, 303, 309, 315, 321, 327, 333, 339, 357, 369, 375, 381, 393, 399, 411, 429, 435, 447, 453, 459, 465, 483, 489, 495, 501, 513, 519 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Define the alternating sum S(u) = sum_{k=0..u} (1-(-1)^k*k) = A064455(u+1) as in A162886.

Evaluate the sum with upper limits u= 1,9, 15, 21... from A014076, and add S(u) to this sequence here whenever it is itself a member of A014076.

LINKS

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

EXAMPLE

The sequence S(u) = 3, 15, 24, 33, 39, 42, 51, 54, 60, 69, ... is generated by u = 1, 9, 15, 21, ...

The first S-term, 3, is prime, and therefore not added to the sequence. The second S-term, 15, is an odd nonprime and added to the sequence. The third, 24, is even and not added to the sequence.

CROSSREFS

Cf. A014076.

Sequence in context: A141230 A140608 A085371 * A231370 A246755 A212311

Adjacent sequences:  A162884 A162885 A162886 * A162888 A162889 A162890

KEYWORD

nonn,less

AUTHOR

Juri-Stepan Gerasimov, Jul 16 2009

EXTENSIONS

3 removed by R. J. Mathar, Aug 27 2009

STATUS

approved

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Last modified May 6 05:03 EDT 2021. Contains 343580 sequences. (Running on oeis4.)