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
Offset: 0
Examples
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
Links
Crossrefs
Cf. A062884.
Extensions
More terms and better description from John W. Layman, Nov 01 2001
Further terms from Jud McCranie, Nov 01 2001