

A153588


Number of resistance values that can be constructed using up to n equal resistances by arranging them in an arbitrary seriesparallel arrangement.


14



1, 3, 7, 15, 35, 77, 179, 429, 1039, 2525, 6235, 15463, 38513, 96231, 241519, 607339, 1529533, 3857447, 9743247, 24634043, 62335495, 157885967, 400211085, 1015080877, 2576308943
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OFFSET

1,2


LINKS

Table of n, a(n) for n=1..25.
Antoni Amengual, The intriguing properties of the equivalent resistances of n equal resistors combined in series and in parallel, American Journal of Physics, 68(2), 175179 (February 2000).
Sameen Ahmed Khan, Mathematica notebook for A153588 and A058351
Sameen Ahmed Khan, The bounds of the set of equivalent resistances of n equal resistors combined in series and in parallel, EPrint arXiv:1004.3346 (21 April 2010).
S. A. Khan, How Many Equivalent Resistances?, RESONANCE, May 2012.  From N. J. A. Sloane, Oct 15 2012
M. Ortolano, M. Abrate, L. Callegaro, On the synthesis of Quantum Hall Array Resistance Standards, arXiv preprint arXiv:1311.0756, 2013
Project Euler, Problem 155


EXAMPLE

Example: For n=2 there are 3 solutions, 1 ohm, (1+1) ohms and 1/(1/1+1/1)=1/2 ohm.


CROSSREFS

Cf. A048211. This sequence is the total number of resistance values formed using up to n resistances, A048211 is the total number of resistance values formed using exactly n resistances.
A048211, A153588, A174283, A174284, A174285 and A174286, A176497, A176498, A176499, A176500, A176501, A176502 [From Sameen Ahmed Khan, Apr 27 2010]
Sequence in context: A147379 A213722 A217092 * A221945 A077946 A077970
Adjacent sequences: A153585 A153586 A153587 * A153589 A153590 A153591


KEYWORD

hard,more,nonn


AUTHOR

Altrego Janeway (altrego99(AT)gmail.com), Dec 29 2008


EXTENSIONS

a(17)a(25) from Antoine Mathys, Apr 02 2015
Definition clarified by Antoine Mathys, Apr 03 2015


STATUS

approved



