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 A111573 a(n) = a(n-1) + a(n-3) + a(n-4), n >= 4. 6
 0, 1, 3, 3, 4, 8, 14, 21, 33, 55, 90, 144, 232, 377, 611, 987, 1596, 2584, 4182, 6765, 10945, 17711, 28658, 46368, 75024, 121393, 196419, 317811, 514228, 832040, 1346270, 2178309, 3524577, 5702887, 9227466, 14930352, 24157816, 39088169 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS See comment and FAMP code for A111569. Many of these are also Fibonacci numbers (A000045), including 1, 3, 8, 21, 55, 144, 377, 987, 2584, 6765, 17711, 46368, 121393, 317811, 832040, ... and many differ from a Fibonacci number by 1. Why? a(30) and a(31) are both divisible by 2207. Similarly, a(32) and a(33) are both divisible by 3571. Why? - Jonathan Vos Post, Aug 10 2005 LINKS Index entries for linear recurrences with constant coefficients, signature (1,0,1,1) FORMULA G.f. -x*(1+2*x)/((x^2+x-1)*(x^2+1)) a(n) = A056594(n+3)+A000045(n+1). [From R. J. Mathar, Nov 10 2009] PROG Floretion Algebra Multiplication Program, FAMP Code: -2kbaseseq[B+H] with B = - .25'i + .25'j - .25i' + .25j' + k' - .5'kk' - .25'ik' - .25'jk' - .25'ki' - .25'kj' - .5e and H = + .75'ii' + .75'jj' + .75'kk' + .75e CROSSREFS Cf. A001638, A111569, A111570, A111571, A111572, A111574, A111575, A111576. Sequence in context: A155822 A160646 A019466 * A049854 A291872 A195978 Adjacent sequences:  A111570 A111571 A111572 * A111574 A111575 A111576 KEYWORD easy,nonn AUTHOR Creighton Dement, Aug 10 2005 STATUS approved

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Last modified January 18 01:05 EST 2020. Contains 330995 sequences. (Running on oeis4.)