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 A121343 a(n) = Fibonacci(n) mod n(n+1)/2. 4
 0, 0, 1, 2, 3, 5, 8, 13, 21, 34, 0, 23, 66, 51, 62, 10, 35, 67, 19, 1, 45, 89, 1, 229, 168, 275, 298, 236, 319, 59, 155, 125, 309, 376, 407, 485, 630, 628, 419, 466, 615, 370, 517, 343, 663, 830, 988, 1033, 168, 624, 700, 746, 1167, 158, 872, 1105, 609, 610, 59, 1181, 0, 1, 125 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,4 LINKS Alois P. Heinz, Table of n, a(n) for n = 0..10000 FORMULA A000045(n) modulo A000217(n). EXAMPLE a(11)=23 since Fib(11)=89==23(mod (11*12/2)). MAPLE a:= proc(n) local r, M, p, m; r, M, p, m:=       <<1|0>, <0|1>>, <<0|1>, <1|1>>, n, n*(n+1)/2;       do if irem(p, 2, 'p')=1 then r:= r.M mod m fi;          if p=0 then break fi; M:= M.M mod m       od; r[1, 2]     end: seq(a(n), n=0..100);  # Alois P. Heinz, Nov 26 2016 MATHEMATICA f[n_] := If[n == 0, 0, Mod[Fibonacci@n, n(n + 1)/2]]; f /@ Range[0, 62] (* Robert G. Wilson v, Aug 31 2006 *) Join[{0}, Mod[First[#], Last[#]]&/@With[{nn=70}, Thread[{Fibonacci[ Range[ nn]], Accumulate[Range[nn]]}]]] (* Harvey P. Dale, May 21 2012 *) PROG (PARI) fibmod(n, m)=((Mod([1, 1; 1, 0], m))^n)[1, 2] a(n)=lift(fibmod(n, n*(n+1)/2)) \\ Charles R Greathouse IV, Jun 20 2017 CROSSREFS Cf. A000045, A023173, A000217, A096535. Sequence in context: A280198 A175712 A013986 * A321021 A236768 A023439 Adjacent sequences:  A121340 A121341 A121342 * A121344 A121345 A121346 KEYWORD nonn,easy AUTHOR N. J. A. Sloane, Aug 29 2006 EXTENSIONS Edited by N. J. A. Sloane, Jul 01 2008 at the suggestion of R. J. Mathar STATUS approved

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Last modified May 12 11:51 EDT 2021. Contains 343821 sequences. (Running on oeis4.)