A053263
Coefficients of the '5th-order' mock theta function chi_1(q).
Original entry on oeis.org
1, 2, 2, 3, 3, 4, 4, 6, 5, 7, 8, 9, 9, 12, 12, 15, 15, 18, 19, 23, 23, 27, 30, 33, 34, 41, 42, 49, 51, 57, 61, 69, 72, 81, 87, 96, 100, 113, 119, 132, 140, 153, 163, 180, 188, 208, 221, 240, 253, 278, 294, 319, 339, 366, 388, 422, 443, 481, 510, 549, 580, 626, 662
Offset: 0
From _Gus Wiseman_, Apr 20 2023: (Start)
The a(1) = 1 through a(8) = 6 partitions such that 2*(minimum) > (maximum):
(1) (2) (3) (4) (5) (6) (7) (8)
(11) (111) (22) (32) (33) (43) (44)
(1111) (11111) (222) (322) (53)
(111111) (1111111) (332)
(2222)
(11111111)
The a(1) = 1 through a(8) = 6 partitions such that (median) = (maximum):
(1) (2) (3) (4) (5) (6) (7) (8)
(11) (111) (22) (221) (33) (331) (44)
(1111) (11111) (222) (2221) (332)
(111111) (1111111) (2222)
(22211)
(11111111)
(End)
- Srinivasa Ramanujan, Collected Papers, Chelsea, New York, 1962, pp. 354-355
- Srinivasa Ramanujan, The Lost Notebook and Other Unpublished Papers, Narosa Publishing House, New Delhi, 1988, pp. 20, 25
- Vaclav Kotesovec, Table of n, a(n) for n = 0..5000 (terms 0..1000 from Seiichi Manyama)
- George E. Andrews, The fifth and seventh order mock theta functions, Trans. Amer. Math. Soc., 293 (1986) 113-134.
- George E. Andrews and Frank G. Garvan, Ramanujan's "lost" notebook VI: The mock theta conjectures, Advances in Mathematics, 73 (1989) 242-255.
- George N. Watson, The mock theta functions (2), Proc. London Math. Soc., series 2, 42 (1937) 274-304.
Other '5th-order' mock theta functions are at
A053256,
A053257,
A053258,
A053259,
A053260,
A053261,
A053262,
A053264,
A053265,
A053266,
A053267.
-
1+Series[Sum[q^(2n+1)(1+q^n)/Product[1-q^k, {k, n+1, 2n+1}], {n, 0, 49}], {q, 0, 100}]
(* Also: *)
Table[Count[ IntegerPartitions[n], p_ /; 2 Min[p] > Max[p]], {n, 40}]
(* Clark Kimberling, Feb 16 2014 *)
nmax = 100; CoefficientList[Series[1 + Sum[x^(2*k+1)*(1+x^k) / Product[1-x^j, {j, k+1, 2*k+1}], {k, 0, Floor[nmax/2]}], {x, 0, nmax}], x] (* Vaclav Kotesovec, Jun 12 2019 *)
A361856
Positive integers whose prime indices satisfy (maximum) = 2*(median).
Original entry on oeis.org
12, 24, 42, 48, 60, 63, 72, 96, 126, 130, 140, 144, 189, 192, 195, 252, 266, 288, 308, 325, 330, 360, 378, 384, 399, 420, 432, 495, 546, 567, 572, 576, 588, 600, 630, 638, 650, 665, 756, 768, 819, 864, 882, 884, 931, 945, 957, 962, 975, 1122, 1134, 1152, 1190
Offset: 1
The terms together with their prime indices begin:
12: {1,1,2}
24: {1,1,1,2}
42: {1,2,4}
48: {1,1,1,1,2}
60: {1,1,2,3}
63: {2,2,4}
72: {1,1,1,2,2}
96: {1,1,1,1,1,2}
126: {1,2,2,4}
130: {1,3,6}
140: {1,1,3,4}
144: {1,1,1,1,2,2}
The prime indices of 126 are {1,2,2,4}, with maximum 4 and median 2, so 126 is in the sequence.
The prime indices of 308 are {1,1,4,5}, with maximum 5 and median 5/2, so 308 is in the sequence.
The LHS (greatest prime index) is
A061395.
These partitions are counted by
A361849.
A000975 counts subsets with integer median.
-
prix[n_]:=If[n==1,{}, Flatten[Cases[FactorInteger[n],{p_,k_}:>Table[PrimePi[p],{k}]]]];
Select[Range[100],Max@@prix[#]==2*Median[prix[#]]&]
A361848
Number of integer partitions of n such that (maximum) <= 2*(median).
Original entry on oeis.org
1, 2, 3, 5, 6, 9, 12, 15, 19, 26, 31, 40, 49, 61, 75, 93, 112, 137, 165, 199, 238, 289, 341, 408, 482, 571, 674, 796, 932, 1096, 1280, 1495, 1738, 2026, 2347, 2724, 3148, 3639, 4191, 4831, 5545, 6372, 7298, 8358, 9552, 10915, 12439, 14176, 16121, 18325
Offset: 0
The a(1) = 1 through a(7) = 12 partitions:
(1) (2) (3) (4) (5) (6) (7)
(11) (21) (22) (32) (33) (43)
(111) (31) (41) (42) (52)
(211) (221) (51) (61)
(1111) (2111) (222) (322)
(11111) (321) (331)
(2211) (421)
(21111) (2221)
(111111) (3211)
(22111)
(211111)
(1111111)
For example, the partition y = (3,2,2) has maximum 3 and median 2, and 3 <= 2*2, so y is counted under a(7).
For length instead of median we have
A237755.
For minimum instead of median we have
A237824.
For mean instead of median we have
A361851.
A000975 counts subsets with integer median.
Cf.
A008284,
A013580,
A027193,
A061395,
A067538,
A111907,
A240219,
A324562,
A359907,
A361394,
A361860.
A361851
Number of integer partitions of n such that (length) * (maximum) <= 2*n.
Original entry on oeis.org
1, 2, 3, 5, 7, 11, 12, 18, 23, 31, 37, 51, 58, 75, 96, 116, 126, 184, 193, 253, 307, 346, 402, 511, 615, 678, 792, 1045, 1088, 1386, 1419, 1826, 2181, 2293, 2779, 3568, 3659, 3984, 4867, 5885, 6407, 7732, 8124, 9400, 11683, 13025, 13269, 16216, 17774, 22016
Offset: 1
The a(1) = 1 through a(7) = 12 partitions:
(1) (2) (3) (4) (5) (6) (7)
(11) (21) (22) (32) (33) (43)
(111) (31) (41) (42) (52)
(211) (221) (51) (61)
(1111) (311) (222) (322)
(2111) (321) (331)
(11111) (411) (421)
(2211) (2221)
(3111) (3211)
(21111) (22111)
(111111) (211111)
(1111111)
The partition y = (3,2,1,1) has length 4 and maximum 3, and 4*3 <= 2*7, so y is counted under a(7).
The partition y = (5,2,1,1) has length 4 and maximum 5, and 4*5 is not <= 2*9, so y is not counted under a(9).
The partition y = (3,2,1,1) has diagram:
o o o
o o .
o . .
o . .
with complement of size 5, and 5 <= 7, so y is counted under a(7).
For length instead of mean we have
A237755.
For minimum instead of mean we have
A237824.
For median instead of mean we have
A361848.
A051293 counts subsets with integer mean.
A067538 counts partitions with integer mean.
Cf.
A111907,
A237984,
A240219,
A324521,
A324562,
A327482,
A349156,
A360068,
A360071,
A360241,
A361394,
A361859.
A361859
Number of integer partitions of n such that the maximum is greater than or equal to twice the median.
Original entry on oeis.org
0, 0, 0, 1, 2, 3, 7, 10, 15, 23, 34, 46, 67, 90, 121, 164, 219, 285, 375, 483, 622, 799, 1017, 1284, 1621, 2033, 2537, 3158, 3915, 4832, 5953, 7303, 8930, 10896, 13248, 16071, 19451, 23482, 28272, 33977, 40736, 48741, 58201, 69367, 82506, 97986, 116139
Offset: 1
The a(4) = 1 through a(9) = 15 partitions:
(211) (311) (411) (421) (422) (522)
(2111) (3111) (511) (521) (621)
(21111) (3211) (611) (711)
(4111) (4211) (4221)
(22111) (5111) (4311)
(31111) (32111) (5211)
(211111) (41111) (6111)
(221111) (33111)
(311111) (42111)
(2111111) (51111)
(321111)
(411111)
(2211111)
(3111111)
(21111111)
The partition y = (5,2,2,1) has maximum 5 and median 2, and 5 >= 2*2, so y is counted under a(10).
For length instead of median we have
A237752.
For minimum instead of median we have
A237821.
Reversing the inequality gives
A361848.
The complement is counted by
A361858.
These partitions have ranks
A361868.
For mean instead of median we have
A361906.
A000975 counts subsets with integer median.
Cf.
A008284,
A027193,
A067538,
A237755,
A237820,
A237824,
A240219,
A359907,
A361851,
A361860,
A361907.
A361908
Positive integers > 1 whose prime indices satisfy (maximum) = 2*(minimum).
Original entry on oeis.org
6, 12, 18, 21, 24, 36, 48, 54, 63, 65, 72, 96, 105, 108, 133, 144, 147, 162, 189, 192, 216, 288, 315, 319, 324, 325, 384, 432, 441, 455, 481, 486, 525, 567, 576, 648, 715, 731, 735, 768, 845, 864, 931, 945, 972, 1007, 1029, 1152, 1296, 1323, 1403, 1458, 1463
Offset: 1
The terms together with their prime indices begin:
6: {1,2}
12: {1,1,2}
18: {1,2,2}
21: {2,4}
24: {1,1,1,2}
36: {1,1,2,2}
48: {1,1,1,1,2}
54: {1,2,2,2}
63: {2,2,4}
65: {3,6}
72: {1,1,1,2,2}
96: {1,1,1,1,1,2}
The RHS is 2*
A055396 (twice minimum).
The LHS is
A061395 (greatest prime index).
Partitions of this type are counted by
A118096.
A001221 (omega) counts distinct prime factors.
A001222 (bigomega) counts prime factors with multiplicity.
-
filter:= proc(n) local F,b;
if n::even then b:= padic:-ordp(n,3);
if b = 0 then return false else return n = 2^padic:-ordp(n,2) * 3^b fi
fi;
F:= ifactors(n)[2][..,1];
nops(F) >= 2 and numtheory:-pi(max(F)) = 2*numtheory:-pi(min(F))
end proc:
select(filter, [$1..2000]); # Robert Israel, Mar 11 2025
-
Select[Range[2,100],PrimePi[FactorInteger[#][[-1,1]]]==2*PrimePi[FactorInteger[#][[1,1]]]&]
A361907
Number of integer partitions of n such that (length) * (maximum) > 2*n.
Original entry on oeis.org
0, 0, 0, 0, 0, 0, 3, 4, 7, 11, 19, 26, 43, 60, 80, 115, 171, 201, 297, 374, 485, 656, 853, 1064, 1343, 1758, 2218, 2673, 3477, 4218, 5423, 6523, 7962, 10017, 12104, 14409, 17978, 22031, 26318, 31453, 38176, 45442, 55137, 65775, 77451, 92533, 111485, 131057
Offset: 1
The a(7) = 3 through a(10) = 11 partitions:
(511) (611) (711) (721)
(4111) (5111) (5211) (811)
(31111) (41111) (6111) (6211)
(311111) (42111) (7111)
(51111) (52111)
(411111) (61111)
(3111111) (421111)
(511111)
(3211111)
(4111111)
(31111111)
The partition y = (3,2,1,1) has length 4 and maximum 3, and 4*3 is not > 2*7, so y is not counted under a(7).
The partition y = (4,2,1,1) has length 4 and maximum 4, and 4*4 is not > 2*8, so y is not counted under a(8).
The partition y = (5,1,1,1) has length 4 and maximum 5, and 4*5 > 2*8, so y is counted under a(8).
The partition y = (5,2,1,1) has length 4 and maximum 5, and 4*5 > 2*9, so y is counted under a(9).
The partition y = (3,2,1,1) has diagram:
o o o
o o .
o . .
o . .
with complement (shown in dots) of size 5, and 5 is not > 7, so y is not counted under a(7).
Reversing the inequality gives
A361852.
A051293 counts subsets with integer mean.
A116608 counts partitions by number of distinct parts.
Cf.
A027193,
A111907,
A237752,
A237755,
A237821,
A237824,
A237984,
A324562,
A326622,
A327482,
A349156,
A360071,
A361394.
A361852
Number of integer partitions of n such that (length) * (maximum) < 2n.
Original entry on oeis.org
1, 2, 3, 5, 7, 9, 12, 17, 21, 27, 37, 41, 58, 67, 80, 106, 126, 153, 193, 209, 263, 326, 402, 419, 565, 650, 694, 891, 1088, 1120, 1419, 1672, 1987, 2245, 2345, 2856, 3659, 3924, 4519, 4975, 6407, 6534, 8124, 8280, 9545, 12937, 13269, 13788, 16474, 20336
Offset: 1
The a(1) = 1 through a(7) = 12 partitions:
(1) (2) (3) (4) (5) (6) (7)
(11) (21) (22) (32) (33) (43)
(111) (31) (41) (42) (52)
(211) (221) (51) (61)
(1111) (311) (222) (322)
(2111) (321) (331)
(11111) (2211) (421)
(21111) (2221)
(111111) (3211)
(22111)
(211111)
(1111111)
For example, the partition y = (3,2,1,1) has length 4 and maximum 3, and 4*3 < 2*7, so y is counted under a(7).
For length instead of mean we have
A237754.
For median instead of mean we have
A361858.
The complement is counted by
A361906.
Reversing the inequality gives
A361907.
A051293 counts subsets with integer mean.
A067538 counts partitions with integer mean.
Cf.
A027193,
A111907,
A116608,
A237824,
A237984,
A324517,
A327482,
A349156,
A360068,
A360071,
A361394.
A361857
Number of integer partitions of n such that the maximum is greater than twice the median.
Original entry on oeis.org
0, 0, 0, 0, 1, 2, 3, 7, 11, 16, 25, 37, 52, 74, 101, 138, 185, 248, 325, 428, 554, 713, 914, 1167, 1476, 1865, 2336, 2922, 3633, 4508, 5562, 6854, 8405, 10284, 12536, 15253, 18489, 22376, 26994, 32507, 39038, 46802, 55963, 66817, 79582, 94643, 112315
Offset: 1
The a(5) = 1 through a(10) = 16 partitions:
(311) (411) (511) (521) (522) (622)
(3111) (4111) (611) (621) (721)
(31111) (4211) (711) (811)
(5111) (5211) (5221)
(32111) (6111) (5311)
(41111) (33111) (6211)
(311111) (42111) (7111)
(51111) (43111)
(321111) (52111)
(411111) (61111)
(3111111) (331111)
(421111)
(511111)
(3211111)
(4111111)
(31111111)
The partition y = (5,2,2,1) has maximum 5 and median 2, and 5 > 2*2, so y is counted under a(10).
For length instead of median we have
A237751.
For minimum instead of median we have
A237820.
The complement is counted by
A361848.
Reversing the inequality gives
A361858.
These partitions have ranks
A361867.
For mean instead of median we have
A361907.
A000975 counts subsets with integer median.
A361867
Positive integers > 1 whose prime indices satisfy (maximum) > 2*(median).
Original entry on oeis.org
20, 28, 40, 44, 52, 56, 66, 68, 76, 78, 80, 84, 88, 92, 99, 102, 104, 112, 114, 116, 117, 120, 124, 132, 136, 138, 148, 152, 153, 156, 160, 164, 168, 170, 171, 172, 174, 176, 184, 186, 188, 190, 198, 200, 204, 207, 208, 212, 220, 222, 224, 228, 230, 232, 234
Offset: 1
The prime indices of 84 are {1,1,2,4}, with maximum 4 and median 3/2, and 4 > 2*(3/2), so 84 is in the sequence.
The terms together with their prime indices begin:
20: {1,1,3}
28: {1,1,4}
40: {1,1,1,3}
44: {1,1,5}
52: {1,1,6}
56: {1,1,1,4}
66: {1,2,5}
68: {1,1,7}
76: {1,1,8}
78: {1,2,6}
80: {1,1,1,1,3}
84: {1,1,2,4}
88: {1,1,1,5}
92: {1,1,9}
99: {2,2,5}
The LHS is
A061395 (greatest prime index).
For mean instead of median we have
A361907.
A000975 counts subsets with integer median.
-
prix[n_]:=If[n==1,{},Flatten[Cases[FactorInteger[n], {p_,k_}:>Table[PrimePi[p],{k}]]]];
Select[Range[100], Max@@prix[#]>2*Median[prix[#]]&]
Showing 1-10 of 13 results.
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