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A069518 Geometric mean of digits = 4 and digits are in nondecreasing order. 4

%I #12 Apr 29 2021 00:57:08

%S 4,28,44,188,248,444,1488,2288,2448,4444,12888,14488,22488,24448,

%T 44444,118888,124888,144488,222888,224488,244448,444444,1148888,

%U 1228888,1244888,1444488,2224888,2244488,2444448,4444444,11288888,11448888,12248888,12444888

%N Geometric mean of digits = 4 and digits are in nondecreasing order.

%C No number is obtainable by permuting the digits of other members - only one with ascending order of digits is included.

%H Michael S. Branicky, <a href="/A069518/b069518.txt">Table of n, a(n) for n = 1..10000</a>

%e 1488 is a term but 1848 is not.

%t a = {}; b = 4; Do[c = Apply[ Times, IntegerDigits[n]]/b^Floor[ Log[10, n] + 1]; If[c == 1 && Position[a, FromDigits[ Sort[ IntegerDigits[n]]]] == {}, Print[n]; a = Append[a, n]], {n, 1, 10^7}]

%o (Python)

%o from math import prod

%o from sympy.utilities.iterables import multiset_combinations

%o def auptod(terms):

%o n, digits, alst, powsexps2 = 0, 1, [], [(1, 0), (2, 1), (4, 2), (8, 3)]

%o while n < terms:

%o target = 4**digits

%o mcstr = "".join(str(d)*(digits//max(1, r//2)) for d, r in powsexps2)

%o for mc in multiset_combinations(mcstr, digits):

%o if prod(map(int, mc)) == target:

%o n += 1

%o alst.append(int("".join(mc)))

%o if n == terms: break

%o else: digits += 1

%o return alst

%o print(auptod(34)) # _Michael S. Branicky_, Apr 28 2021

%Y Cf. A061428, A069512, A069516.

%K nonn,base

%O 1,1

%A _Amarnath Murthy_, Mar 30 2002

%E Edited and extended by _Robert G. Wilson v_, Apr 01 2002

%E Name edited and a(31) and beyond from _Michael S. Branicky_, Apr 28 2021

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Last modified March 28 20:05 EDT 2024. Contains 371254 sequences. (Running on oeis4.)