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Let f(n) be 2n + POD(n) + 1 if n is even, otherwise 2n - POD(n) - 1, where POD(n) is the product of digits of n. Sequence gives smallest number requiring n iterations to reach a prime.
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%I #5 Dec 15 2017 17:36:03

%S 2,1,13,8,9,34,86,51,113,348,193,152,80,199,736,579,448,502,446,281,

%T 339,532,1521,760,438,371,971,524,1642,988,1613,6856,4494,5146,2793,

%U 1348,3916,5531,6544,3570,7982,6415,3211,1633,11634,9462

%N Let f(n) be 2n + POD(n) + 1 if n is even, otherwise 2n - POD(n) - 1, where POD(n) is the product of digits of n. Sequence gives smallest number requiring n iterations to reach a prime.

%e a(3) = 13 because 13 -(1)-> 22 -(2)-> 49 -(3)-> 61.

%K base,nonn

%O 1,1

%A _Jason Earls_, Sep 08 2002