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A124400 a(0)=1, a(1)=1, a(2)=4, a(3)=7, a(n) = a(n-1) + 3*a(n-2) - a(n-4) for n>=4. 17
1, 1, 4, 7, 18, 38, 88, 195, 441, 988, 2223, 4992, 11220, 25208, 56645, 127277, 285992, 642615, 1443946, 3244514, 7290360, 16381287, 36808421, 82707768, 185842671, 417584688, 938304280, 2108350576, 4737420745, 10644887785, 23918845740 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

Unsigned version of A077920.

The sequence is the INVERT transform of the aerated even-indexed Fibonacci numbers (i.e., of (1, 0, 3, 0, 8, 0,...)). Sequence A131322 is the INVERT transform of the aerated odd-indexed Fibonacci numbers. - Gary W. Adamson, Feb 07 2014

LINKS

Table of n, a(n) for n=0..30.

FORMULA

G.f.: 1/(1-x-3*x^2+x^4).

CROSSREFS

Cf. A131322.

Sequence in context: A219498 A219754 A289975 * A077920 A234269 A135582

Adjacent sequences:  A124397 A124398 A124399 * A124401 A124402 A124403

KEYWORD

easy,nonn

AUTHOR

Philippe Deléham, Dec 14 2006

STATUS

approved

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Last modified February 24 11:12 EST 2018. Contains 299603 sequences. (Running on oeis4.)