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 A020995 Numbers n such that the sum of the digits of Fibonacci(n) is n. 6
 0, 1, 5, 10, 31, 35, 62, 72, 175, 180, 216, 251, 252, 360, 494, 504, 540, 946, 1188, 2222 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS Since the number of digits in the n-th Fibonacci number ~ n*log_10(Golden Ratio), theoretically this sequence is infinite, but then the average density of those digits = ~ 0.208987. - Robert G. Wilson v Robert Dawson of Saint Mary's University says it is likely that 2222 is the last term, as (assuming that the digits are equally distributed) the expected digit sum is ~ 0.9*n. - Stefan Steinerberger, Mar 12 2006 Bankoff's short paper lists the first seven terms. - T. D. Noe, Mar 19 2012 No more terms < 150000. - Manfred Scheucher, Aug 03 2015 If it exists, a(21) > 10^6. - Robert Price, May 26 2019 REFERENCES Alfred S. Posamentier & Ingmar Lehmann, The (Fabulous) Fibonacci Numbers, Prometheus Books, NY, 2007, page 209. LINKS Leon Bankoff, A Fibonacci Curiosity, Fibonacci Quarterly 14, Feb. 1976, p. 17. Pat Ballew, Fibonacci Digit Sums, Pat's Blog, Sunday, 5 August 2012. Manfred Scheucher, Sage Script David Terr, On the Sums of Digits of Fibonacci Numbers, Fibonacci Quarterly 34, Aug. 1996, pp. 349-355. EXAMPLE Fibonacci(10) = 55 and 5+5 = 10. MATHEMATICA Do[ If[ Apply[ Plus, IntegerDigits[ Fibonacci[n]]] == n, Print[n]], {n, 1, 10^5} ] (* Sven Simon *) Do[ If[ Mod[ Fibonacci[n], 9] == Mod[n, 9], If[ Plus @@ IntegerDigits[ Fibonacci[n]] == n, Print[n]]], {n, 0, 10^6}] (* Robert G. Wilson v *) Select[Range[0, 10^5], Plus @@ IntegerDigits[Fibonacci[ # ]] == # &] (* Ron Knott, Oct 30 2010 *) PROG (PARI) isok(n) = sumdigits(fibonacci(n)) == n; \\ Michel Marcus, Feb 18 2015 CROSSREFS Cf. A000045, A067515, A004090. Sequence in context: A056422 A032296 A052648 * A174467 A005201 A221304 Adjacent sequences:  A020992 A020993 A020994 * A020996 A020997 A020998 KEYWORD nonn,base,more AUTHOR STATUS approved

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Last modified April 11 08:59 EDT 2021. Contains 342886 sequences. (Running on oeis4.)