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A068909
Number of partitions of n modulo 7.
3
1, 1, 2, 3, 5, 0, 4, 1, 1, 2, 0, 0, 0, 3, 2, 1, 0, 3, 0, 0, 4, 1, 1, 2, 0, 5, 0, 0, 1, 1, 4, 3, 5, 0, 4, 1, 1, 0, 3, 0, 0, 0, 2, 2, 2, 3, 5, 0, 0, 2, 1, 4, 0, 0, 0, 0, 3, 2, 2, 3, 5, 0, 4, 2, 2, 2, 3, 5, 0, 4, 3, 2, 4, 6, 5, 0, 0, 2, 2, 4, 3, 5, 0, 0, 3, 3, 6, 6, 3, 0, 1, 3, 3, 4, 3, 5, 0, 0, 4, 3, 4, 6, 5, 0, 1
OFFSET
0,3
COMMENTS
Of the partitions of numbers from 1 to 100000: 27193 are 0, 12078 are 1, 12203 are 2, 12260 are 3, 12231 are 4, 12003 are 5 and 12032 are 6 modulo 7, largely because the number of partitions of 7m+5 is always a multiple of 7.
FORMULA
a(n) = A010876(A000041(n)) = A068906(7, n).
a(n) = Pm(n,1) with Pm(n,k) = if k<n then (Pm(n-k,k) + Pm(n,k+1)) mod 7 else 0^(n*(k-n)). [Reinhard Zumkeller, Jun 09 2009]
MATHEMATICA
Table[Mod[PartitionsP[n], 7], {n, 0, 110}] (* Harvey P. Dale, Feb 17 2018 *)
PROG
(PARI) a(n) = numbpart(n) % 7; \\ Michel Marcus, Jul 14 2022
CROSSREFS
KEYWORD
nonn
AUTHOR
Henry Bottomley, Mar 05 2002
STATUS
approved