A134071 Primes in A134072.

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

Table of n, a(n) for n=1..4.

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

Adjacent sequences: A134068 A134069 A134070 * A134072 A134073 A134074

Keyword

hard,more,nonn,base

Author

Alexander Adamchuk, Oct 06 2007

Extensions

Edited by Charles R Greathouse IV, Apr 24 2010

Status

approved