A370810 Numbers n such that only one set can be obtained by choosing a different divisor of each prime index of n.
1, 2, 6, 9, 10, 22, 25, 30, 34, 42, 45, 62, 63, 66, 75, 82, 98, 99, 102, 110, 118, 121, 134, 147, 153, 166, 170, 186, 210, 218, 230, 246, 254, 275, 279, 289, 310, 314, 315, 330, 343, 354, 358, 363, 369, 374, 382, 390, 402, 410, 422, 425, 462, 482, 490, 495
Offset: 1
Keywords
Examples
The prime indices of 6591 are {2,6,6,6}, for which the only choice is {1,2,3,6}, so 6591 is in the sequence. The terms together with their prime indices begin: 1: {} 2: {1} 6: {1,2} 9: {2,2} 10: {1,3} 22: {1,5} 25: {3,3} 30: {1,2,3} 34: {1,7} 42: {1,2,4} 45: {2,2,3} 62: {1,11} 63: {2,2,4} 66: {1,2,5} 75: {2,3,3} 82: {1,13} 98: {1,4,4} 99: {2,2,5} 102: {1,2,7} 110: {1,3,5}
Crossrefs
A000005 counts divisors.
Programs
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Mathematica
prix[n_]:=If[n==1,{},Flatten[Cases[FactorInteger[n], {p_,k_}:>Table[PrimePi[p],{k}]]]]; Select[Range[100],Length[Union[Sort /@ Select[Tuples[Divisors/@prix[#]],UnsameQ@@#&]]]==1&]
Comments