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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.
3
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
OFFSET
0,2
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
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