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A338197 a(n) is the number of distinct resistances that can be obtained by a network of exactly n equal resistors, but not by any network with fewer than n equal resistors. 16

%I

%S 1,2,4,8,20,44,114,312,894,2639,8005,24362,74918,231123,722388,

%T 2276599,7242497,23144119

%N a(n) is the number of distinct resistances that can be obtained by a network of exactly n equal resistors, but not by any network with fewer than n equal resistors.

%C See A180414 and A337517 for more information and references.

%H Allan Gottlieb, <a href="https://cs.nyu.edu/~gottlieb/tr/overflow/2003-oct-3-more.html">Oct 3, 2003 addendum (Karnofsky)</a>.

%H <a href="/index/Res#resistances">Index to sequences related to resistances</a>.

%F a(n) = A180414(n) - A180414(n-1).

%F a(n) = A051389(n) for n <= 5, a(n) > A051389(n) otherwise.

%e a(6) = 44 because the resistances 11/13 and 13/11 (in units of resistor value) are representable in addition to the A051389(6)=42 resistances that can be achieved by only serial and parallel configurations with exactly 6 resistors and not by a network with fewer than 6 resistors.

%Y Cf. A051389, A180414, A337517, A338487.

%K nonn,hard,more

%O 1,2

%A _Hugo Pfoertner_, Nov 03 2020

%E a(15) corrected and a(16) added by _Hugo Pfoertner_, Dec 06 2020

%E a(17) from _Hugo Pfoertner_, Dec 09 2020

%E a(18) from _Hugo Pfoertner_, Apr 09 2021

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Last modified July 29 14:59 EDT 2021. Contains 346346 sequences. (Running on oeis4.)