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A339124
a(n) is the number of squares at distance n from the central square of a golden square fractal.
2
1, 4, 12, 28, 60, 132, 300, 692, 1596, 3668, 8412, 19284, 44220, 101428, 232668, 533716, 1224252, 2808180, 6441372, 14775188, 33891324, 77739956, 178319964, 409030356, 938233788, 2152120564, 4936534044, 11323421716, 25973664636, 59578391604
OFFSET
0,2
COMMENTS
For symmetry reasons, a(n) is a multiple of 4 for any n > 0.
FORMULA
G.f.: (2*x^4 - 2*x^2 - x - 1)/(2*x^4 - 2*x^2 + 3*x - 1).
a(0) = 1.
a(n) = A269962(n+1) - A269962(n) for any n > 0.
a(n) = 3*a(n-1) - 2*a(n-2) + 2*a(n-4) for n > 4. - Stefano Spezia, Dec 02 2020
CROSSREFS
See A337018 for similar sequences.
Cf. A269962 (partial sums).
Sequence in context: A269712 A028399 A173033 * A317233 A309917 A034508
KEYWORD
nonn,easy
AUTHOR
Rémy Sigrist, Nov 24 2020
STATUS
approved