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 A225974 Multiplicative persistence with squares of decimal digits: smallest number such that the number of iterations of "multiply digits squared" needed to reach 0 or 1 equals n. 2
 0, 10, 25, 28, 29, 32, 41 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS This sequence is probably finite. The number of times you need to multiply the square of the digits together before reaching 0 or 1 is equals to n. LINKS EXAMPLE a(4)=  29 -> 4*81 = 324 -> 9*4*16 = 576 -> 25*49*36 = 44100 -> 0 has persistence 4. MATHEMATICA lst = {}; n = 0; Do[While[True, k = n; c = 0; While[k > 9, k = Times @@ IntegerDigits[k]^2; c++]; If[c == l, Break[]]; n++]; AppendTo[lst, n], {l, 0, 7}]; lst CROSSREFS Cf. A003001, A031348, A031349. Sequence in context: A048195 A133634 A174051 * A274046 A014090 A154057 Adjacent sequences:  A225971 A225972 A225973 * A225975 A225976 A225977 KEYWORD nonn,hard,fini,base AUTHOR Michel Lagneau, May 22 2013 STATUS approved

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Last modified January 21 22:54 EST 2021. Contains 340359 sequences. (Running on oeis4.)