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A026356
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a(n) = floor((n-1)*phi) + n + 1, n > 0, where phi = (1+sqrt(5))/2.
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10
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2, 4, 7, 9, 12, 15, 17, 20, 22, 25, 28, 30, 33, 36, 38, 41, 43, 46, 49, 51, 54, 56, 59, 62, 64, 67, 70, 72, 75, 77, 80, 83, 85, 88, 91, 93, 96, 98, 101, 104, 106, 109, 111, 114, 117, 119, 122, 125, 127, 130, 132, 135, 138, 140, 143, 145
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OFFSET
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1,1
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COMMENTS
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Greatest k such that s(k) = n+1, where s = A026354.
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LINKS
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MATHEMATICA
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PROG
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(PARI) r = (1 + sqrt(5))/2;
a(n) = if(n<1, 1, floor((n - 1)* r) + n + 1);
(Python)
from sympy import sqrt
import math
r=(1 + sqrt(5))/2
def a(n): return 1 if n<1 else int(math.floor((n - 1)*r)) + n + 1
(Python)
from math import isqrt
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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