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 A017921 Powers of sqrt(5) rounded up. 3
 1, 3, 5, 12, 25, 56, 125, 280, 625, 1398, 3125, 6988, 15625, 34939, 78125, 174693, 390625, 873465, 1953125, 4367321, 9765625, 21836602, 48828125, 109183007, 244140625, 545915034, 1220703125, 2729575168 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Vincenzo Librandi, Table of n, a(n) for n = 0..1000 EXAMPLE sqrt(5)^3 = 11.18033988749895... so a(3) = 12. sqrt(5)^4 = 25, so a(4) = 25. sqrt(5)^5 = 55.90169943749474241... so a(5) = 56. MATHEMATICA Ceiling[Sqrt[5]^Range[0, 40]] (* Vincenzo Librandi, Nov 20 2011 *) PROG (Magma) [Ceiling(Sqrt(5^n)): n in [0..40]]; // Vincenzo Librandi, Nov 20 2011 (PARI) a(n) = ceil(sqrt(5^n)); \\ Michel Marcus, Dec 14 2017 (Python) from math import isqrt def A017921(n): return isqrt(5**n)+(n&1) # Chai Wah Wu, Jun 19 2024 CROSSREFS Cf. A017919, A017920. Sequence in context: A129757 A135019 A141685 * A280000 A241097 A267725 Adjacent sequences: A017918 A017919 A017920 * A017922 A017923 A017924 KEYWORD nonn,easy AUTHOR N. J. A. Sloane STATUS approved

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Last modified August 6 04:44 EDT 2024. Contains 374957 sequences. (Running on oeis4.)