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A322968 Number of integer partitions of n with no ones whose parts are all powers of the same squarefree number.

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%I A322968 #20 Jan 23 2025 20:05:42
%S A322968 1,0,1,1,2,1,4,1,4,2,6,1,9,1,8,4,10,1,14,1,16,5,16,1,24,2,22,5,28,1,
%T A322968 37,1,36,7,38,4,55,1,48,9,63,1,73,1,76,12,76,1,105,2,98,11,116,1,128,
%U A322968 5,143,14,142,1,186,1,168,18,202,5,223,1,240,17,247,1,305,1,286,23
%N A322968 Number of integer partitions of n with no ones whose parts are all powers of the same squarefree number.
%C A322968 First differs from A072721 at a(12) = 9, A072721(12) = 10.
%C A322968 First differs from A379957 at a(16) = 10, A379957(16) = 9.
%H A322968 Andrew Howroyd, <a href="/A322968/b322968.txt">Table of n, a(n) for n = 0..10000</a>
%H A322968 <a href="/index/Par#part">Index entries for sequences related to partitions</a>.
%F A322968 From  _Andrew Howroyd_, Jan 23 2025: (Start)
%F A322968 G.f.: 1 + Sum_{k>=2} -1 + 1/Product_{j>=1} (1 - x^(A005117(k)^j)).
%F A322968 a(p) = 1 for prime p. (End)
%e A322968 The a(2) = 1 through a(12) = 9 integer partitions (A = 10, B = 11):
%e A322968   (2)  (3)  (4)   (5)  (6)    (7)  (8)     (9)    (A)      (B)  (66)
%e A322968             (22)       (33)        (44)    (333)  (55)          (84)
%e A322968                        (42)        (422)          (82)          (93)
%e A322968                        (222)       (2222)         (442)         (444)
%e A322968                                                   (4222)        (822)
%e A322968                                                   (22222)       (3333)
%e A322968                                                                 (4422)
%e A322968                                                                 (42222)
%e A322968                                                                 (222222)
%e A322968 The a(20) = 16 integer partitions:
%e A322968   (10,10), (16,4),
%e A322968   (8,8,4), (16,2,2),
%e A322968   (5,5,5,5), (8,4,4,4), (8,8,2,2),
%e A322968   (4,4,4,4,4), (8,4,4,2,2),
%e A322968   (4,4,4,4,2,2), (8,4,2,2,2,2),
%e A322968   (4,4,4,2,2,2,2), (8,2,2,2,2,2,2),
%e A322968   (4,4,2,2,2,2,2,2),
%e A322968   (4,2,2,2,2,2,2,2,2),
%e A322968   (2,2,2,2,2,2,2,2,2,2).
%t A322968 radbase[n_]:=n^(1/GCD@@FactorInteger[n][[All,2]]);
%t A322968 powsqfQ[n_]:=SameQ@@Last/@FactorInteger[n];
%t A322968 Table[Length[Select[IntegerPartitions[n],And[FreeQ[#,1],And@@powsqfQ/@#,SameQ@@radbase/@#]&]],{n,30}]
%o A322968 (PARI) a(n)={if(n==0, 1, sumdiv(n, d, if(d>1&&issquarefree(d), polcoef(1/prod(j=1, logint(n, d), 1 - x^(d^j), Ser(1, x, 1+n)), n))))} \\ _Andrew Howroyd_, Jan 23 2025
%o A322968 (PARI) seq(n)={Vec(1 + sum(d=2, n, if(issquarefree(d), -1 + 1/prod(j=1, logint(n, d), 1 - x^(d^j), Ser(1, x, 1+n)))))} \\ _Andrew Howroyd_, Jan 23 2025
%Y A322968 Cf. A001597, A005117, A018819, A023893, A052410, A072720, A072721, A072774, A102430, A322900, A322903, A322911, A322912, A379957.
%K A322968 nonn
%O A322968 0,5
%A A322968 _Gus Wiseman_, Jan 01 2019
%E A322968 a(66) onwards from _Andrew Howroyd_, Jan 23 2025