login
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.
0
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
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: A052526 A366921 A306498 * A233403 A054293 A072859
KEYWORD
nonn,base,easy
AUTHOR
J. Lowell, Sep 12 2011
EXTENSIONS
a(1) prepended by Zak Seidov, Sep 18 2011
STATUS
approved