|
Search: id:A118877
|
|
|
| A118877 |
|
Determinant of n-th continuous block of 4 consecutive composites. |
|
+0
1
|
|
| -12, -12, 6, 6, -18, -18, 12, 12, -24, -24, 18, -3, -28, -2, -2, 24, 24, -36, -36, -2, -2, 32, -3, -42, 36, 36, -48, -48, 42, -3, -52, -2, -2, 48, -3, -58, -2, -2, 54, 54, -66, -66, -2, -2, 62, -3, -72, 66, 66, -78, -78, -2, -2, 74, -3, -84, 78, -3, -88, -2, -2
(list; graph; listen)
|
|
|
OFFSET
|
1,1
|
|
|
COMMENT
|
Composites analogue of A117301 Determinants of 2 X 2 matrices of continuous blocks of 4 consecutive primes. See also: A118780 Determinants of 2 X 2 matrices of continuous blocks of 4 consecutive semiprimes. The terminology "continuous" is used to distinguish from "discrete" which would be (in this composites case) block 1: 4, 6, 8, 9; block 2: 10, 12, 14, 15, and so forth. It isn't until a(12) that we break the pattern of a(2n)=a(2n-1); there seem to be strangely many such pairs of two identical values. a(12) is also the first odd value in the sequence, and the first prime.
|
|
FORMULA
|
a(n) = A002808(n)*A002808(n+3) - A002808(n+1)*A002808(n+2).
|
|
EXAMPLE
|
a(1) = -12 =
|4 6|
|8 9|.
|
|
CROSSREFS
|
Cf. A002808, A117301, A118780.
Adjacent sequences: A118874 A118875 A118876 this_sequence A118878 A118879 A118880
Sequence in context: A038337 A125509 A097824 this_sequence A112124 A069873 A129498
|
|
KEYWORD
|
easy,sign
|
|
AUTHOR
|
Jonathan Vos Post (jvospost2(AT)yahoo.com), May 24 2006
|
|
|
Search completed in 0.002 seconds
|
