A162887 Odd nonprimes in an alternating 1-based sum up to some odd nonprime.

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

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