A023811 Largest metadrome (number with digits in strict ascending order) in base n.
0, 1, 5, 27, 194, 1865, 22875, 342391, 6053444, 123456789, 2853116705, 73686780563, 2103299351334, 65751519677857, 2234152501943159, 81985529216486895, 3231407272993502984, 136146740744970718253, 6106233505124424657789, 290464265927977839335179
Offset: 1
Examples
a(5) = 1234[5] (in base 5) = 1*5^3 + 2*5^2 + 3*5 + 4 = 125 + 50 + 15 + 4 = 194. a(10) = 123456789 (in base 10).
Links
- Vincenzo Librandi, Table of n, a(n) for n = 1..200
- Christian Perfect, Integer sequence reviews on Numberphile (or vice versa), 2013.
- Chai Wah Wu, Pandigital and penholodigital numbers, arXiv:2403.20304 [math.GM], 2024. See p. 1.
Programs
-
Haskell
a023811 n = foldl (\val dig -> val * n + dig) 0 [0 .. n - 1] -- Reinhard Zumkeller, Aug 29 2014
-
Magma
[0] cat [(n^n-n^2+n-1)/(n-1)^2: n in [2..20]]; // Vincenzo Librandi, May 22 2012
-
Maple
0, seq((n^n-n^2+n-1)/(n-1)^2, n=2..100); # Robert Israel, Dec 13 2015
-
Mathematica
Table[Total[(#1 n^#2) & @@@ Transpose@ {Range[n - 1], Reverse@ (Range[n - 1] - 1)}], {n, 20}] (* Michael De Vlieger, Jul 24 2015 *) Table[Sum[(b - k)*b^(k - 1), {k, b - 1}], {b, 30}] (* Clark Kimberling, Aug 22 2015 *) Table[FromDigits[Range[0, n - 1], n], {n, 20}] (* L. Edson Jeffery, Dec 13 2015 *)
-
PARI
{for(i=1,18,cuo=0; for(j=1,i-1,cuo=cuo+j*i^(i-j-1)); print1(cuo,", "))} \\\ Douglas Latimer, May 16 2012
-
PARI
A023811(n)=if(n>1,(n^n-n^2)\(n-1)^2+1) \\ M. F. Hasler, Jan 22 2013
-
Python
def a(n): return (n**n - n**2 + n - 1)//((n - 1)**2) if n > 1 else 0 print([a(n) for n in range(1, 21)]) # Michael S. Branicky, Apr 24 2023
Formula
a(n) = Sum_{j=1...n-1} j*n^(n-1-j).
lim_{n->infinity} a(n)/a(n-1) - a(n-1)/a(n-2) = exp(1). - Conjectured by Gerald McGarvey, Sep 26 2004. Follows from the formula below and lim_{n->infinity} (1+1/n)^n = e. - Franklin T. Adams-Watters, Jan 25 2010
a(n) = (n^n-n^2+n-1)/(n-1)^2 = A058128(n)-1 = n*A060073(n)-1 (for n>=2). - Henry Bottomley, Feb 21 2001
Extensions
Edited by M. F. Hasler, Jan 22 2013
Comments