A046511 Numbers with multiplicative persistence value 2.
25, 26, 27, 28, 29, 34, 35, 36, 37, 38, 43, 44, 45, 46, 48, 52, 53, 54, 56, 58, 62, 63, 64, 65, 67, 72, 73, 76, 82, 83, 84, 85, 92, 99, 125, 126, 127, 128, 129, 134, 135, 136, 137, 138, 143, 144, 145, 146, 148, 152, 153, 154, 156, 158, 162, 163, 164, 165, 167, 172
Offset: 1
Examples
129 -> [ 18 ] -> [ 8 ] = one digit in two steps.
Links
- Daniel Mondot, Table of n, a(n) for n = 1..10000 (terms 1..3000 from Vincenzo Librandi)
- Eric Weisstein's World of Mathematics, Multiplicative Persistence
Programs
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Mathematica
mpQ[n_]:=Length[NestWhileList[Times@@IntegerDigits[#]&,n,#>9&]]==3; Select[Range[200], mpQ] (* Harvey P. Dale, Apr 12 2014 *)
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Python
from math import prod def pd(n): return prod(map(int, str(n))) def ok(n): return n > 9 and (p := pd(n)) > 9 and pd(p) < 10 print([k for k in range(173) if ok(k)]) # Michael S. Branicky, Jan 16 2022
Comments