A080213 a(n) = binomial(n, greatest prime factor of n).

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

Robin Visser, Table of n, a(n) for n = 1..3000

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

Cf. A006530, A080211, A080212.

Sequence in context: A064083 A152249 A167580 * A200091 A180733 A334504

Adjacent sequences: A080210 A080211 A080212 * A080214 A080215 A080216

Keyword

nonn

Author

Reinhard Zumkeller, Feb 06 2003

Status

approved