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A047208
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Numbers that are congruent to {0, 4} mod 5.
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28
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0, 4, 5, 9, 10, 14, 15, 19, 20, 24, 25, 29, 30, 34, 35, 39, 40, 44, 45, 49, 50, 54, 55, 59, 60, 64, 65, 69, 70, 74, 75, 79, 80, 84, 85, 89, 90, 94, 95, 99, 100, 104, 105, 109, 110, 114, 115, 119, 120, 124, 125, 129, 130, 134, 135, 139, 140, 144, 145, 149
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OFFSET
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1,2
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COMMENTS
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Also solutions to 3^x + 5^x == 2 (mod 11). - Cino Hilliard, May 18 2003
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LINKS
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FORMULA
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G.f.: x^2*(4+x)/((1-x)^2*(1+x)).
a(n) = a(n-2) + 5. (End)
Sum_{n>=2} (-1)^n/a(n) = log(5)/4 + log(phi)/(2*sqrt(5)) - sqrt(1+2/sqrt(5))*Pi/10, where phi is the golden ratio (A001622). - Amiram Eldar, Dec 07 2021
E.g.f.: 1 + ((5*x - 7/2)*exp(x) + (3/2)*exp(-x))/2. - David Lovler, Aug 23 2022
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MATHEMATICA
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{#, #+4}&/@(5*Range[0, 30])//Flatten (* Harvey P. Dale, Apr 05 2019 *)
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PROG
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(Magma) [(5*(n-1) + 3*((n-1) mod 2))/2: n in [1..100]]; // G. C. Greubel, Nov 23 2021
(Sage) [(5*(n-1) +3*((n-1)%2))/2 for n in (1..100)] # G. C. Greubel, Nov 23 2021
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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