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A239799 a(n) = gcd(Sum_{k=1...n} L(k), Product_{j=1...n} L(j)), where L(k) is the k-th Lucas number. 0
1, 1, 4, 3, 2, 44, 1, 24, 28, 319, 14, 168, 1, 2204, 16, 231, 2, 15124, 1, 1584, 4, 103679, 2, 4176, 7, 710644, 56, 28623, 2, 4870844, 1, 150024, 4, 33385279, 2, 205656, 101, 228826124, 256, 269247, 14, 1568397604, 49, 9227232, 4, 10749957119, 2, 24157728, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Observation: For k = 1,2,... the numbers L(4k)-3 = 4, 44, 319, 2204, 15124, 103679, 710644, 4870844, 33385279,... are in the sequence.

LINKS

Table of n, a(n) for n=1..49.

EXAMPLE

The first 6 Lucas numbers are 1, 3, 4, 7, 11, 18 => 1+3+4+7+11+18 = 44. So a(6) = gcd(44, 1*3*4*7*11*18) = 44.

MAPLE

with(combinat, fibonacci):a:=n->2*fibonacci(n-1)+fibonacci(n): seq(gcd(add(a(i), i=1..n), mul(a(j), j=1..n)), n=1..50);

MATHEMATICA

nn=60; With[{prs=LucasL[Range[nn]]}, Table[GCD[Total[Take[prs, n]], Times@@Take[ prs, n]], {n, nn}]]

CROSSREFS

Cf. A000204, A239740.

Sequence in context: A019130 A245348 A174551 * A305235 A120011 A177924

Adjacent sequences:  A239796 A239797 A239798 * A239800 A239801 A239802

KEYWORD

nonn

AUTHOR

Michel Lagneau, Mar 27 2014

STATUS

approved

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Last modified August 11 18:37 EDT 2020. Contains 336428 sequences. (Running on oeis4.)