A134072 -id:A134072 - cp's OEIS frontend

A134071 Primes in A134072.

31, 431, 117431, 19912376472918117431

Offset: 1

Alexander Adamchuk, Oct 06 2007

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

			a(1) = A134072(2) = 31.
a(2) = A134072(3) = 431.
a(3) = A134072(5) = 117431.

Eric Weisstein's World of Mathematics, Lucas Number
Eric Weisstein's World of Mathematics, Smarandache Sequences

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).

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 *)

Edited by Charles R Greathouse IV, Apr 24 2010

A134070 Primes in A130774.

Original entry on oeis.org

13, 13471118294776123, 134711182947761231993225218431364220735715778934915127244763960364079103682167761271443439204710647114985118604983010349

Offset: 1

Alexander Adamchuk, Oct 06 2007

A130774 = {1, 13, 134, 1347, 134711, 13471118, 1347111829, 134711182947, 13471118294776, 13471118294776123, ...} = Concatenate Lucas numbers. Indices of prime terms in A130774 are {2, 10, 31, ...}.

a(4) > A130774(500) = 1.347...*10^26425, if it exists. - Amiram Eldar, Jul 17 2025

			a(1) = A130774(2) = 13.
a(2) = A130774(10) = 13471118294776123.
a(3) = A130774(31) = 13471118294776123199322521843136422073571577893491512724476396036407910368216776127144343920471064711498511860498301034.

Eric Weisstein's World of Mathematics, Lucas Number.
Eric Weisstein's World of Mathematics, Smarandache Sequences.

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. A134071 (primes in A134072).

Select[Module[{nn=40,ll},ll=LucasL[Range[nn]];Table[FromDigits[Flatten[IntegerDigits/@Take[ll,n]]],{n,nn}]],PrimeQ] (* Harvey P. Dale, May 07 2023 *)

Edited by Charles R Greathouse IV, Apr 24 2010

cp's OEIS Frontend

A134071 Primes in A134072.

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