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A001573 Another approximation to A000084(n).
(Formerly M1190 N0460)
2
1, 2, 4, 9, 23, 63, 177, 514, 1527, 4625, 14230, 44357, 139779, 444558, 1425151, 4600339, 14939849, 48778197, 160019885, 527200711 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Appears to have been calculated with very low precision. A093156 is a better version. - Pab Ter (pabrlos(AT)yahoo.com), May 11 2004

REFERENCES

J. Riordan and C. E. Shannon, The number of two-terminal series-parallel networks, J. Math. Phys., 21 (1942), 83-93. Reprinted in Claude Elwood Shannon: Collected Papers, edited by N. J. A. Sloane and A. D. Wyner, IEEE Press, NY, 1993, pp. 560-570.

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

LINKS

Table of n, a(n) for n=1..20.

J. Riordan and C. E. Shannon, The number of two-terminal series-parallel networks (annotated scanned copy)

CROSSREFS

Cf. A000084, A058585.

Sequence in context: A274882 A127384 A058585 * A135307 A000083 A092668

Adjacent sequences:  A001570 A001571 A001572 * A001574 A001575 A001576

KEYWORD

nonn,more

AUTHOR

N. J. A. Sloane

STATUS

approved

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Last modified March 28 15:38 EDT 2017. Contains 284243 sequences.