A353507 Product of multiplicities of the prime exponents (signature) of n; a(1) = 0.
0, 1, 1, 1, 1, 2, 1, 1, 1, 2, 1, 1, 1, 2, 2, 1, 1, 1, 1, 1, 2, 2, 1, 1, 1, 2, 1, 1, 1, 3, 1, 1, 2, 2, 2, 2, 1, 2, 2, 1, 1, 3, 1, 1, 1, 2, 1, 1, 1, 1, 2, 1, 1, 1, 2, 1, 2, 2, 1, 2, 1, 2, 1, 1, 2, 3, 1, 1, 2, 3, 1, 1, 1, 2, 1, 1, 2, 3, 1, 1, 1, 2, 1, 2, 2, 2, 2
Offset: 1
Keywords
Examples
The prime signature of 13860 is (2,2,1,1,1), with multiplicities (2,3), so a(13860) = 6.
Links
- Robert Israel, Table of n, a(n) for n = 1..10000
Crossrefs
Programs
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Maple
f:= proc(n) local M,s; M:= ifactors(n)[2][..,2]; mul(numboccur(s,M),s=convert(M,set)); end proc: f(1):= 0: map(f, [$1..100]); # Robert Israel, May 19 2023
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Mathematica
Table[If[n==1,0,Times@@Length/@Split[Sort[Last/@FactorInteger[n]]]],{n,100}] Join[{0},Table[Times@@(Length/@Split[FactorInteger[n][[;;,2]]]),{n,2,100}]] (* Harvey P. Dale, Oct 20 2024 *)
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Python
from math import prod from itertools import groupby from sympy import factorint def A353507(n): return 0 if n == 1 else prod(len(list(g)) for k, g in groupby(factorint(n).values())) # Chai Wah Wu, May 20 2022
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