A340920 a(n) is the number of distinct resistances that can be produced from a planar circuit with exactly n unit resistors.
1, 1, 2, 4, 9, 23, 57, 151, 427, 1263, 3807, 11549, 34843, 104459, 311317, 928719, 2776247, 8320757, 24967341, 74985337
Offset: 0
Examples
a(10) = 3807, whereas A337517(10) = 3823. The difference of 16 resistances results from the 15 terms of A338601/A338602 and the resistance 34/27 not representable by a planar network of 10 resistors, whereas it (but not 27/34) can be represented by a nonplanar network of 10 resistors.
Links
- Stuart Anderson, Catalogues of Simple Perfect Squared Rectangles (SPSR).
- Stuart Anderson, Simple Imperfect Squared Rectangles, orders 9 to 24.
Crossrefs
Programs
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PARI
Replace the list of 3-connected graphs corresponding to A338511 by the list of planar graphs provided in A002840 in Andrew Howroyd's PARI program linked in A180414.
Extensions
a(19) from Hugo Pfoertner, Mar 15 2021