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The least integer with cost n, using the cost function used in sequence A354914.
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%I #28 Feb 16 2023 12:09:47

%S 1,2,3,7,23,719,1169951

%N The least integer with cost n, using the cost function used in sequence A354914.

%C The values up to 1169951 were computed by Joseph DeVincentis, Stan Wagon, and Al Zimmermann. The values appear to rise roughly quadratically, so the next one might be near 10^12 and impossible to find. It is known that the sequence is infinite: that is, the cost function is not bounded.

%e Example: a(4) = 23 because 23 can be reached by the path 1, 2, 3, 4, 5, 20, 23, which has 4 addition steps, and one can check that each smaller number has cost at most 3.

%Y Cf. A354914.

%K nonn,hard,more

%O 0,2

%A _Stan Wagon_, Joseph DeVincentis, and _Al Zimmermann_, Jun 15 2022

%E a(6) corrected by _Stan Wagon_, Feb 15 2023