A093889 a(n) = n!/A093888(n).

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

Offset

0,5

Links

Table of n, a(n) for n=0..29.

Example

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

Prog

(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)
print([a(n) for n in range(34)]) # Michael S. Branicky, Oct 12 2022

Crossrefs

Cf. A000142, A093888.

Sequence in context: A137957 A002514 A319216 * A369085 A020044 A024338

Adjacent sequences: A093886 A093887 A093888 * A093890 A093891 A093892

Keyword

nonn,base

Author

Amarnath Murthy, Apr 23 2004

Extensions

Corrected and extended by Jason Earls, May 07 2004

a(0) and more terms from David A. Corneth, Oct 07 2022

Status

approved