A351295 Numbers whose multiset of prime factors has no permutation with all distinct run-lengths.
6, 10, 14, 15, 21, 22, 26, 30, 33, 34, 35, 36, 38, 39, 42, 46, 51, 55, 57, 58, 60, 62, 65, 66, 69, 70, 74, 77, 78, 82, 84, 85, 86, 87, 90, 91, 93, 94, 95, 100, 102, 105, 106, 110, 111, 114, 115, 118, 119, 120, 122, 123, 126, 129, 130, 132, 133, 134, 138, 140
Offset: 1
Keywords
Examples
The terms together with their prime indices begin: 6: (2,1) 46: (9,1) 84: (4,2,1,1) 10: (3,1) 51: (7,2) 85: (7,3) 14: (4,1) 55: (5,3) 86: (14,1) 15: (3,2) 57: (8,2) 87: (10,2) 21: (4,2) 58: (10,1) 90: (3,2,2,1) 22: (5,1) 60: (3,2,1,1) 91: (6,4) 26: (6,1) 62: (11,1) 93: (11,2) 30: (3,2,1) 65: (6,3) 94: (15,1) 33: (5,2) 66: (5,2,1) 95: (8,3) 34: (7,1) 69: (9,2) 100: (3,3,1,1) 35: (4,3) 70: (4,3,1) 102: (7,2,1) 36: (2,2,1,1) 74: (12,1) 105: (4,3,2) 38: (8,1) 77: (5,4) 106: (16,1) 39: (6,2) 78: (6,2,1) 110: (5,3,1) 42: (4,2,1) 82: (13,1) 111: (12,2) For example, the prime indices of 150 are {1,2,3,3}, with permutations and run-lengths (right): (3,3,2,1) -> (2,1,1) (3,3,1,2) -> (2,1,1) (3,2,3,1) -> (1,1,1,1) (3,2,1,3) -> (1,1,1,1) (3,1,3,2) -> (1,1,1,1) (3,1,2,3) -> (1,1,1,1) (2,3,3,1) -> (1,2,1) (2,3,1,3) -> (1,1,1,1) (2,1,3,3) -> (1,1,2) (1,3,3,2) -> (1,2,1) (1,3,2,3) -> (1,1,1,1) (1,2,3,3) -> (1,1,2) Since none have all distinct run-lengths, 150 is in the sequence.
Crossrefs
These partitions appear to be counted by A351293.
A032020 = number of binary expansions with distinct run-lengths.
A044813 = numbers whose binary expansion has all distinct run-lengths.
A165413 = number of distinct run-lengths in binary expansion.
A181819 = Heinz number of prime signature (prime shadow).
A297770 = number of distinct runs in binary expansion.
Programs
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Mathematica
Select[Range[100],Select[Permutations[Join@@ ConstantArray@@@FactorInteger[#]],UnsameQ@@Length/@Split[#]&]=={}&]
Extensions
Name edited by Gus Wiseman, Aug 13 2025
Comments