A062885 - OEIS

A062885

Smallest multiple of n with property that digits are even and each digit is two less (mod 10) than the previous digit, if such a multiple exists; otherwise -1.

0, 2, 2, 6, 4, 20, 6, 42, 8, 864, 20, 42086, 420, 208, 42, 420, 64, 8642086, 864, 642086, 20, 42, 42086, 6420864, 864, -1, 208, 864, 420, 8642, 420, 86420864208642, 64, 420864208642086, 8642086, 420, 864, 86420864208642, 642086, 86420864208642086420864208642, -1, 642086420864208642, 42, 86, 2086420864, 6420864208642086420, 6420864, 2086420864208642086, 864, 208642, -1, 864208642086420864208642086420864

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OFFSET

0,2

LINKS

Table of n, a(n) for n=0..51.

Don Reble, Analysis of this sequence

Index entries for sequences related to final digits of numbers

EXAMPLE

a(7) = 42 = 7*6 has decreasing even digits.

For n = 25, the conditions require that the desired multiple 25k have k even, i.e., 25k = 25(2i) = 50i = (5i)(10). Thus the final digit is 0, so the next-to-last digit must be 2, but this is impossible since 5i always ends in 0 or 5. Thus a(25) = -1. - John W. Layman, Nov 01 2001

CROSSREFS

Cf. A062884.

Sequence in context: A067045 A083467 A061807 * A062293 A317368 A259882

Adjacent sequences: A062882 A062883 A062884 * A062886 A062887 A062888

KEYWORD

base,easy,nice,sign

AUTHOR

Amarnath Murthy, Jun 28 2001

EXTENSIONS

More terms and better description from John W. Layman, Nov 01 2001

Further terms from Jud McCranie, Nov 01 2001

STATUS

approved