Harmonic Number Sum Congruence
Leroy Quet
qq-quet at mindspring.com
Thu Jan 15 04:47:04 CET 2004
Robert G. Wilson wrote:
> I get:
>1, 4, 16, 73, 388, 2396, 17024, 137544, 1248816, 12603288, 140018688,
>1698063552,
>22318009344, 315942698880, 4791898275840, 77510315197440, 1331759355586560,
>24220225133061120, 464796175236710400, 9385769913543475200, ..., using:
>Table[ Sum[ HarmonicNumber[k]k!(m - k)!, {k, 1, m}], {m, 1, 20}]
>
> Whereas the original seq:
>1, 1, 0, 3, 4, 2, 0, 6, 6, 5, 0, 3, 8, 0, 0, 13, 0, 3, 0, 0, 12, 17, 0, 0,
>14, 0,
>0, 1, 0, 6, 0, 0, 18, 0, 0, 1, 20, 0, 0, 23, 0, 25, 0, 0, 24, 44, 0, 0, 0,
>0, 0,
>36, 0, 0, 0, 0, 30, 8, 0, 36, 32, 0, 0, 0, 0, 10, 0, 0, 0, 2, ..., using:
>Table[ Mod[ Sum[ HarmonicNumber[k]k!(m - k)!, {k, 1, m}], m + 1], {m, 1, 70}]
Thanks for figuring above.
I realize now that the zeros in the mod-sequence become more frequent.
For instance, if (m+1)|(m-1)!!
((m-1)!! = (m-1)(m-3)(m-5)...),
then
the corresponding term in the mod-sequence is zero.
(And it MAY be zero in additional situations too.)
thanks,
Leroy Quet
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