A033180 Numbers k such that k! contains k as a string of digits.
1, 2, 4, 20, 21, 26, 30, 33, 37, 39, 42, 44, 45, 48, 51, 52, 53, 56, 59, 60, 64, 65, 67, 68, 69, 72, 75, 78, 79, 80, 81, 82, 83, 84, 88, 91, 93, 94, 95, 96, 97, 98, 99, 116, 124, 134, 136, 140, 141, 149, 164, 165, 166, 170, 174, 180, 186, 188, 196, 198, 200, 202, 205
Offset: 1
Links
- Mia Boudreau, Table of n, a(n) for n = 1..10000 (First 1000 terms from T. D. Noe)
- Index entries for sequences related to factorial numbers
Programs
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Haskell
a033180 n = a033180_list !! (n-1) a033180_list = filter ((> 0) . a067109) [1..] -- Reinhard Zumkeller, Aug 28 2014
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Mathematica
Select[Range[210],MemberQ[Partition[IntegerDigits[#!],IntegerLength[#], 1], IntegerDigits[ #]]&] (* Harvey P. Dale, Dec 25 2011 *) Select[Range@500, StringContainsQ[ToString[#!], ToString[#]] &] (* Ivan N. Ianakiev, Jul 28 2016 *) Select[Range[210],SequenceCount[IntegerDigits[#!],IntegerDigits[#]]>0&] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Aug 14 2017 *)
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Python
from math import factorial def ok(n): return str(n) in str(factorial(n)) print(list(filter(ok, range(206)))) # Michael S. Branicky, Aug 07 2021
Formula
A067109(a(n)) > 0. - Reinhard Zumkeller, Aug 23 2008
Extensions
More terms from David W. Wilson
Comments