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A080213
a(n) = binomial(n, greatest prime factor of n).
3
1, 1, 1, 6, 1, 20, 1, 28, 84, 252, 1, 220, 1, 3432, 3003, 120, 1, 816, 1, 15504, 116280, 705432, 1, 2024, 53130, 10400600, 2925, 1184040, 1, 142506, 1, 496, 193536720, 2333606220, 6724520, 7140, 1, 35345263800, 8122425444, 658008, 1, 26978328, 1
OFFSET
1,4
COMMENTS
For n>1: a(n)=1 iff n is prime.
LINKS
FORMULA
a(n) = binomial(n, A006530(n)). - Michel Marcus, May 06 2020
MATHEMATICA
Table[Binomial[n, FactorInteger[n][[-1, 1]]], {n, 50}] (* Harvey P. Dale, Feb 25 2015 *)
PROG
(PARI) a(n) = if (n==1, 1, binomial(n, vecmax(factor(n)[, 1]))); \\ Michel Marcus, May 06 2020
(Sage)
def a(n):
if n==1: return 1
return binomial(n, factor(n)[-1][0]) # Robin Visser, Nov 25 2023
CROSSREFS
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Feb 06 2003
STATUS
approved