sums of mods
Chuck Seggelin
seqfan at plastereddragon.com
Mon May 30 16:41:26 CEST 2005
Here's a little sequence I put together the other day, but I doubt it is
interesting enough for inclusion in the OEIS, and even if it were I don't
know how I would describe it in one sentence. Here's how I compute the
terms:
To compute a(n), take the first n primes and find the first value M (>0)
which is not divisible by any of these primes, but which *is* divisible by
the remainders for each of these primes summed together, or zero if there is
no such M. In other words:
a(1) = first value M which is not divisible by 2, but is divisible by (M mod
2). a(1) = 1.
a(2) = 0.
a(3) = first value M which is not divisible by 2, 3, or 5, but is divisible
by (M mod 2) + (M mod 3) + (M mod 5). a(3) = 119.
a(4) = first value M which is not divisible by 2, 3, 5, or 7, but is
divisible by (M mod 2) + (M mod 3) + (M mod 5) + (M mod 7). a(4) = 649.
The first 21 terms:
1, 0, 119, 649, 13, 493, 989, 667, 4399, 67, 3763, 4819, 4717, 9943, 179,
20437, 15677, 193, 26797, 27977, 21251, 37267, ...
The sequence generally trends upward, but occasionally dips very low when
the sum of the remainders happens to exactly equal a prime (as in 13, 67,
179, 193, ...).
Is such a sequence worth including? If so, what would be the best way to
describe it?
-- Chuck Seggelin
More information about the SeqFan
mailing list