The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A036255 Number of inequivalent strings of 2n+1 digits, when 2 strings are equivalent if turning 1 upside down gives the other. 3

%I #8 Jul 03 2017 07:41:28

%S 9,945,98475,9961125,999024375,99975590625,9999389671875,

%T 999984741328125,99999618530859375,9999990463259765625,

%U 999999761581435546875,99999994039535595703125,9999999850988388427734375,999999996274709703369140625,99999999906867742547607421875

%N Number of inequivalent strings of 2n+1 digits, when 2 strings are equivalent if turning 1 upside down gives the other.

%D De Bruijn, Polya's theory of counting, in Beckenbach, ed., Applied Combinatorial Math., Wiley, 1964 (p. 182).

%H Colin Barker, <a href="/A036255/b036255.txt">Table of n, a(n) for n = 0..450</a>

%H <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (130,-3125,12500).

%F a(n) = 10^(2*n+1) - 5^(2*n+1)/2 + 3*5^n/2.

%F From _Colin Barker_, Jul 03 2017: (Start)

%F G.f.: 3*(3 - 75*x + 1250*x^2) / ((1 - 5*x)*(1 - 25*x)*(1 - 100*x)).

%F a(n) = 130*a(n-1) - 3125*a(n-2) + 12500*a(n-3) for n>2.

%F (End)

%o (PARI) Vec(3*(3 - 75*x + 1250*x^2) / ((1 - 5*x)*(1 - 25*x)*(1 - 100*x)) + O(x^20)) \\ _Colin Barker_, Jul 03 2017

%Y Cf. A036257, A036258.

%K nonn,easy,base

%O 0,1

%A _N. J. A. Sloane_

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified September 8 18:41 EDT 2024. Contains 375753 sequences. (Running on oeis4.)