|
|
A328170
|
|
Number of integer partitions of n whose parts minus 1 are relatively prime.
|
|
12
|
|
|
0, 0, 1, 1, 2, 3, 5, 8, 12, 18, 27, 38, 53, 74, 102, 137, 184, 241, 317, 413, 536, 687, 880, 1112, 1405, 1765, 2215, 2755, 3424, 4229, 5216, 6402, 7847, 9572, 11662, 14148, 17139, 20688, 24940, 29971, 35969, 43044, 51438, 61311, 72985, 86678, 102807, 121675
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
0,5
|
|
COMMENTS
|
A partition is relatively prime if the GCD of its parts is 1. Zeros are ignored when computing GCD, and the empty set has GCD 0.
|
|
LINKS
|
|
|
FORMULA
|
G.f.: Sum_{d>=1} mu(d)*(-1/(1-x) + 1/(Prod_{k>=0} 1 - x^(k*d + 1))). - Andrew Howroyd, Oct 17 2019
|
|
EXAMPLE
|
The a(2) = 1 through a(9) = 18 partitions:
(2) (21) (22) (32) (42) (43) (62) (54)
(211) (221) (222) (52) (332) (63)
(2111) (321) (322) (422) (72)
(2211) (421) (431) (432)
(21111) (2221) (521) (522)
(3211) (2222) (621)
(22111) (3221) (3222)
(211111) (4211) (3321)
(22211) (4221)
(32111) (4311)
(221111) (5211)
(2111111) (22221)
(32211)
(42111)
(222111)
(321111)
(2211111)
(21111111)
|
|
MATHEMATICA
|
Table[Length[Select[IntegerPartitions[n], GCD@@(#-1)==1&]], {n, 0, 30}]
|
|
PROG
|
(PARI) seq(n)=Vec(sum(d=1, n-1, moebius(d)*(-1/(1-x) + 1/prod(k=0, n\d, 1 - x*x^(k*d) + O(x*x^n)))), -(n+1)) \\ Andrew Howroyd, Oct 17 2019
|
|
CROSSREFS
|
The Heinz numbers of these partitions are given by A328168.
Partitions whose parts are relatively prime are A000837.
Partitions whose parts plus 1 are relatively prime are A318980.
The GCD of the prime indices of n, all minus 1, is A328167(n).
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|