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A347180
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Lexicographically earliest sequence of distinct positive integers such that the first digit of a(n) is visible in a(n) * a(n+1).
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3
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1, 10, 11, 12, 9, 21, 2, 6, 16, 7, 25, 5, 3, 13, 8, 23, 4, 26, 17, 30, 31, 14, 15, 34, 39, 24, 18, 45, 32, 41, 28, 19, 22, 33, 40, 35, 38, 36, 37, 29, 42, 20, 46, 27, 47, 52, 49, 50, 43, 48, 51, 54, 64, 44, 55, 53, 65, 56, 63, 58, 61, 60, 66, 57, 62, 59, 67, 68, 69, 72, 76, 75, 73, 79, 82, 71, 70
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,2
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LINKS
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EXAMPLE
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a(1) * a(2) = 1 * 10 = 10;
a(2) * a(3) = 10 * 11 = 110;
a(3) * a(4) = 11 * 12 = 132;
a(4) * a(5) = 12 * 9 = 108;
a(5) * a(6) = 9 * 21 = 189; etc.
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PROG
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(Python)
def aupton(terms):
alst, aset = [1], {1}
while len(alst) < terms:
an, target = 2, str(alst[-1])[0]
while an in aset or target not in str(alst[-1]*an): an += 1
alst.append(an); aset.add(an)
return alst
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CROSSREFS
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KEYWORD
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base,nonn
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AUTHOR
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STATUS
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approved
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