A195201 a(n) is the largest prime factor of the number made by taking the previous term and duplicating the final digit, a(1) = 1.

1, 11, 37, 29, 23, 233, 2333, 23333, 661, 601, 6011, 6679, 997, 907, 313, 241, 2411, 47, 53, 41, 137, 17, 59, 599, 857, 953, 9533, 13619, 19457, 821, 23, 233, 2333, 23333, 661, 601, 6011, 6679, 997, 907, 313, 241, 2411, 47, 53, 41, 137, 17, 59, 599, 857, 953

Offset

1,2

Comments

This sequence is periodic with period (23, 233, 2333, 23333, 661, 601, 6011, 6679, 997, 907, 313, 241, 2411, 47, 53, 41, 137, 17, 59, 599, 857, 953, 9533, 13619, 19457, 821) of length 26.

Links

Table of n, a(n) for n=1..52.

Index entries for linear recurrences with constant coefficients, signature (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1).

Example

Next term after 11 is 37 because 111 = 3*37. Next term after 37 is 29 because 377 = 13*29. Next term after 821 is 23 because 8211 = 3*7*17*23.

Mathematica

NestList[FactorInteger[10#+Mod[#, 10]][[-1, 1]]&, 11, 60](* Zak Seidov, Sep 16 2011*)

Crossrefs

Sequence in context: A191296 A052526 A306498 * A233403 A054293 A072859

Adjacent sequences: A195198 A195199 A195200 * A195202 A195203 A195204

Keyword

nonn,base,easy

Author

J. Lowell, Sep 12 2011

Extensions

a(1) prepended by Zak Seidov, Sep 18 2011

Status

approved