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A162886 Even numbers in an alternating 1-based sum up to some odd nonprime. 1
24, 42, 54, 60, 78, 84, 96, 114, 132, 138, 144, 150, 168, 174, 180, 186, 204, 216, 222, 234, 240, 258, 264, 276, 282, 294, 306, 312, 324, 330, 348, 354, 366, 372, 384, 390, 402, 414, 420, 432, 438, 444, 450, 456, 474, 480, 486, 492, 504, 510, 516, 528, 534, 546, 558, 564 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Define an alternating sum S(n) = Sum_{k=0..n} (1-(-1)^k*k) = A064455(n+1).

The sequence contains this sum evaluated for an upper limit of the odd nonprimes where the sum is even.

LINKS

Table of n, a(n) for n=1..56.

EXAMPLE

S(n) evaluated at n=1, 9, 15, 21, ... (taken from A014076) is 3, 15, 24, 33, 42, 51, etc., where only the even values (i.e., 24, 42, etc.) join the sequence.

MAPLE

A014076 := proc(n) option remember ; if n = 1 then 1; else for a from procname(n-1)+2 by 2 do if not isprime(a) then RETURN(a) ; fi; od: fi; end:

S := proc(n) A064455(A014076(n)+1) ; end:

for n from 1 to 200 do if S(n) mod 2 = 0 then printf("%d, ", S(n)) ; fi; od: # R. J. Mathar, Jul 21 2009

CROSSREFS

Cf. A014076.

Sequence in context: A062910 A098900 A098769 * A274350 A063702 A074975

Adjacent sequences:  A162883 A162884 A162885 * A162887 A162888 A162889

KEYWORD

nonn,less

AUTHOR

Juri-Stepan Gerasimov, Jul 16 2009

EXTENSIONS

Edited and values checked by R. J. Mathar Jul 21 2009

STATUS

approved

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Last modified November 22 10:59 EST 2019. Contains 329389 sequences. (Running on oeis4.)