A208646 Calendar Problem #27, April 2012 Mathematics Teacher.

9861, -1986, 9681, -1896, 8961, -1968, 8691, -1698

Offset

1,1

Comments

The numbers are paired on the basis of rotational symmetry with alternating signs.

Links

Table of n, a(n) for n=1..8.

Margaret Coffey, Editor, Calendar Problem #27, April 2012 Mathematics Teacher, pp. 521, 524.

Example

If you rotate the first number, 9861, 180 degrees about its center, and put a negative sign in front, you get the second number: -1986. Similarly, the third and fourth numbers are rotations of each other, as well as of the fifth and sixth numbers.  Therefore the eighth number is the rotation and negation of the seventh number, 8961, which would be -1698.

Crossrefs

Cf. A045574, A054047.

Sequence in context: A022199 A203809 A257299 * A001230 A238076 A103810

Adjacent sequences: A208643 A208644 A208645 * A208647 A208648 A208649

Keyword

sign,easy,base

Author

Jonathan Vos Post, Mar 01 2012

Status

approved