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A087473 Smallest number that requires n iterations of f(k) to reach a single digit, where f(k) is the product of the two numbers formed from the alternating digits of k. 4
1, 10, 25, 39, 77, 171, 199, 577, 887, 1592, 2682, 3988, 6913, 18747, 39577, 58439, 99428, 173442, 267343, 299137, 574182, 685812, 880543, 1635812, 1974447, 2771717, 18871813, 45797337, 49899368, 58935768 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..29.

EXAMPLE

a(4)= 77 since 77 is the smallest number that requires 4 iterations to reach a single digit: f(77)=7*7=49, f(49)=4*9=36, f(36)=3*6=18, f(18)=1*8=8.

CROSSREFS

Cf. A087471, A087472, A087474.

Sequence in context: A154057 A074814 A002600 * A014120 A003001 A198377

Adjacent sequences:  A087470 A087471 A087472 * A087474 A087475 A087476

KEYWORD

nonn,base

AUTHOR

Amarnath Murthy and Paul D. Hanna, Sep 11 2003

EXTENSIONS

More terms from Ray Chandler, Sep 19 2003

STATUS

approved

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Last modified May 26 21:38 EDT 2018. Contains 304645 sequences. (Running on oeis4.)