204]
ON A PROBLEM IN THE PARTITION OF NUMBERS.
249
and the coefficients 1, 58, (£, ( X), &c. are precisely those of the infinite series 1, 2, 4, 6,
&c. We have more simply
1
+ 23.« + (£« 2 + 2)« 3 + &c. =
1
(1 — X) 2 (1 — X?) (1 — X*) (1 — X 8 ) & c. ’
which gives rise to the following very simple algorithm for the calculation of the
coefficients :
1,
2,
3,
4,
5,
6,
7,
8,
9,
10,
11,
12,
13,
14,
15,
16
0,
0;
1,
2,
4,
6,
9,
12,
16,
20,
25,
30,
36,
42,
49,
56
1,
2,
4,
6,
9,
12,
16,
20,
25,
30,
36,
42,
49,
56,
64,
72
0,
o,
o,
0;
1,
2,
4,
6,
10,
14,
20,
26,
35,
44,
56,
68
1,
2,
4,
6,
10,
14,
20,
26,
35,
44,
56,
68,
84,
100,
120,
140
o,
0,
o,
o,
o,
0,
o,
0;
1,
2,
4,
6,
10,
14,
20,
26
11
2 |
4,
6 1
10,
14,
20,
26 |
36,
46,
60,
74,
94,
114,
140,
166|
&c.
The last line is marked off into periods of (reckoning from the beginning) 1, 2, 4, 8,
&c.; and by what has preceded, the series which gives the number of 1-partitions,
2-partitions, 3-partitions, &c. is found by summing to the end of each period and
doubling the results; we thus, in fact, obtain (1), 2, 6, 26, 166, 1626, &c.: and the
same series is also given by means of the last terms of the several periods.
The preceding expression for 1 + 58« + Gt« 2 + &c. shows that 58, 6, &c. are the
number of partitions of 1, 2, 3, 4, 5, 6, &c. respectively into the parts 1, 1', 2, 4, 8,
&c.: and we are thus led to—
Theorem. The number of «-partitions (first part unity, no part greater than twice
the preceding one) is equal to the number of partitions of 2 a; ~ 1 — 1 into the parts
1, T, 2, 4,... 2 a:-2 . Or, again, it is equal to twice the sum of the number of partitions
of 0, 1, 2,... 2 X ~~— 1 respectively into the parts 1, 1', 2, 4,... 2 X ~ 3 (where the number of
partitions of 0 counts for 1).
For example, the partitions of 0, 1, 2, 3, &c. with the parts 1, 1', 2,... are
(•)
1, V,
1+1, 1 + 1', l'+l', 2,
1+1 + 1, 1 + 1 + 1', l + l' + l', l' + l'+l', 2 + 1, 2+r,
the numbers of which are 1, 2, 4, 6. Hence, by the first part of the theorem, the
number of 3-partitions is 6, and by the second part of the theorem, the number of
4-partitions is
2 (1 + 2 + 4 + 6), = 26.
2, Stone Buildings, March 17, 1857.
C. III.
32