A219187 Sum of distinct prime divisors of Lucas(n).
2, 0, 3, 2, 7, 11, 5, 29, 47, 21, 44, 199, 32, 521, 284, 44, 2207, 3571, 112, 9349, 2168, 242, 353, 600, 1152, 263, 90484, 5800, 14510, 19548, 2567, 3010349, 5568, 10102, 63513, 1022, 103713, 54018521, 29134604, 1461, 4689, 370248451, 1796, 151190, 2118, 785
Offset: 0
Keywords
Examples
a(6) = 5 because Lucas(6) = 21 and the sum of the prime divisors {3, 7} equals 10.
Links
- Amiram Eldar, Table of n, a(n) for n = 0..1000
Programs
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Maple
with (numtheory):with(combinat,fibonacci): sopf:= proc(n) local e, j; e := ifactors(fibonacci(n+1)+fibonacci(n-1))[2]: add (e[j][1], j=1..nops(e)) end: seq (sopf(n), n=0..100);
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Mathematica
Array[If[#==1, 0, Plus@@First/@FactorInteger[LucasL[ # ]]]&, 50, 0]
Formula
Extensions
a(0) prepended by Amiram Eldar, Sep 03 2019