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1, 1, 1, 1, 3, 15, 80, 20, 160, 1440, 75, 825, 9900, 128700, 165888, 2488320, 39813120, 597196800, 10749542400, 125411328000, 2508226560000, 52672757760000, 2769091920000, 4901791334400, 117642992025600, 2941074800640000, 76467944816640000, 2064634510049280000, 57809766281379840000, 1676483222160015360000
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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0,5
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LINKS
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EXAMPLE
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a(4) = 3 as the largest palindromic divisor of 4! comes from the set {1, 2, 3, 4, 6, 8, 12, 24}. The largest palindrome is this set is 8 so a(4) = 4! / 8 = 3. - David A. Corneth, Oct 12 2022
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PROG
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(Python)
from sympy import divisors, factorial, multiplicity
def ispal(n): s = str(n); return s == s[::-1]
def b(f, k): return f//k**multiplicity(k, f)
def a(n):
f = factorial(n)
m2 = max(d for d in divisors(b(f, 2), generator=True) if ispal(d))
m5 = max(d for d in divisors(b(f, 5), generator=True) if ispal(d))
return f//max(m2, m5)
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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