This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A362608 #14 May 04 2023 14:57:32 %S A362608 0,1,2,2,4,5,7,11,16,21,29,43,54,78,102,131,175,233,295,389,490,623, %T A362608 794,1009,1255,1579,1967,2443,3016,3737,4569,5627,6861,8371,10171, %U A362608 12350,14901,18025,21682,26068,31225,37415,44617,53258,63313,75235,89173,105645 %N A362608 Number of integer partitions of n having a unique mode. %C A362608 A mode in a multiset is an element that appears at least as many times as each of the others. For example, the modes of {a,a,b,b,b,c,d,d,d} are {b,d}. %H A362608 Andrew Howroyd, <a href="/A362608/b362608.txt">Table of n, a(n) for n = 0..1000</a> %F A362608 G.f.: Sum_{m>=1} (Sum_{j>=1} x^(j*m)*(1 - x^j)/(1 - x^(j*m))) * (Product_{j>=1} (1 - x^(j*m))/(1 - x^j)). - _Andrew Howroyd_, May 04 2023 %e A362608 The partition (3,3,2,1) has greatest multiplicity 2, and a unique part of multiplicity 2 (namely 3), so is counted under a(9). %e A362608 The a(1) = 1 through a(7) = 11 partitions: %e A362608 (1) (2) (3) (4) (5) (6) (7) %e A362608 (11) (111) (22) (221) (33) (322) %e A362608 (211) (311) (222) (331) %e A362608 (1111) (2111) (411) (511) %e A362608 (11111) (3111) (2221) %e A362608 (21111) (3211) %e A362608 (111111) (4111) %e A362608 (22111) %e A362608 (31111) %e A362608 (211111) %e A362608 (1111111) %t A362608 Table[Length[Select[IntegerPartitions[n],Length[Commonest[#]]==1&]],{n,0,30}] %o A362608 (PARI) seq(n) = my(A=O(x*x^n)); Vec(sum(m=1, n, sum(j=1, n\m, x^(j*m)*(1-x^j)/(1 - x^(j*m)), A)*prod(j=1, n\m, (1 - x^(j*m))/(1 - x^j) + A)/prod(j=n\m+1, n, 1 - x^j + A)), -(n+1)) \\ _Andrew Howroyd_, May 04 2023 %Y A362608 For parts instead of multiplicities we have A000041(n-1), ranks A102750. %Y A362608 For median instead of mode we have A238478, complement A238479. %Y A362608 These partitions have ranks A356862. %Y A362608 The complement is counted by A362607, ranks A362605. %Y A362608 For co-mode complement we have A362609, ranks A362606. %Y A362608 For co-mode we have A362610, ranks A359178. %Y A362608 A275870 counts collapsible partitions. %Y A362608 A359893 counts partitions by median. %Y A362608 A362611 counts modes in prime factorization, co-modes A362613. %Y A362608 A362614 counts partitions by number of modes, co-modes A362615. %Y A362608 Cf. A002865, A008284, A053263, A098859, A237984, A304442, A327472, A360071, A360687, A362612. %K A362608 nonn %O A362608 0,3 %A A362608 _Gus Wiseman_, Apr 30 2023