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A134071
Primes in A134072.
2
31, 431, 117431, 19912376472918117431
OFFSET
1,1
COMMENTS
A134072 = {1, 31, 431, 7431, 117431, 18117431, 2918117431, 472918117431, 76472918117431, 12376472918117431, 19912376472918117431, ...} = concatenation of Lucas numbers in reverse order. Indices of prime terms in A134072 are {2, 3, 5, 11, ...}.
No further terms through 500 Lucas numbers. - Harvey P. Dale, Aug 17 2013
LINKS
Eric Weisstein's World of Mathematics, Lucas Number
Eric Weisstein's World of Mathematics, Smarandache Sequences
EXAMPLE
a(1) = A134072(2) = 31.
a(2) = A134072(3) = 431.
a(3) = A134072(5) = 117431.
MATHEMATICA
nn=500; With[{lucs=LucasL[Range[nn]]}, Select[Table[FromDigits[ Flatten[ IntegerDigits/@ Reverse[ Take[lucs, n]]]], {n, nn}], PrimeQ]] (* Harvey P. Dale, Aug 17 2013 *)
CROSSREFS
Cf. A000204 (Lucas numbers).
Cf. A130774 (concatenation of Lucas numbers).
Cf. A019523 (concatenation of Fibonacci numbers).
Cf. A038399 (concatenation of first n nonzero Fibonacci numbers in reverse order).
Cf. A134072 (concatenation of A000204 Lucas numbers (beginning at 1) in reverse order).
Cf. A134069 (primes in A038399).
Cf. A134070 (primes in A130774).
Sequence in context: A352606 A089561 A134072 * A278964 A010836 A022723
KEYWORD
hard,more,nonn,base
AUTHOR
Alexander Adamchuk, Oct 06 2007
EXTENSIONS
Edited by Charles R Greathouse IV, Apr 24 2010
STATUS
approved