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A046995 Greek-key tours on a 4 X n board; i.e., self-avoiding walks on 4 X n grid starting in top left corner. 6
1, 4, 17, 52, 160, 469, 1337, 3750, 10347, 28249, 76382, 204996, 546651, 1449952, 3828232, 10067585, 26384939, 68941126, 179658343, 467084601, 1211812016, 3138075544, 8112667259, 20941558268, 53983767498 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

REFERENCES

Posting by Thomas Womack (mert0236(AT)sable.ox.ac.uk) to sci.math newsgroup, Apr 21 1999.

LINKS

Table of n, a(n) for n=1..25.

FORMULA

Conjecture: a(n)=3a(n-1)+3a(n-2)-9a(n-3)-6a(n-4)+5a(n-5)+a(n-6)-3a(n-7)+a(n-8) for n>=10. - Dean Hickerson, Apr 05 2003

Conjecture: G.f.: x*(-(x-1)*(x^7-x^6-2*x^5+3*x^4-2*x^3-4*x^2-2*x-1))/((x^4-2*x^3+2*x^2+2*x-1)*(x^4-x^3-3*x^2-x+1)) [From Maksym Voznyy (voznyy(AT)mail.ru), Jul 27 2009]

CROSSREFS

Cf. A046994.

Sequence in context: A047668 A208658 A092091 * A001585 A060262 A157492

Adjacent sequences:  A046992 A046993 A046994 * A046996 A046997 A046998

KEYWORD

nonn,walk

AUTHOR

Antreas P. Hatzipolakis (xpolakis(AT)otenet.gr)

EXTENSIONS

More terms from Hugo van der Sanden, Apr 02 2003

STATUS

approved

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Last modified May 17 05:13 EDT 2021. Contains 343965 sequences. (Running on oeis4.)