A345881 - OEIS

A345881

At digit-position a(n) in the sequence starts the product 2*a(n). This is the lexicographically earliest sequence of distinct positive terms with this property. See the Comments section for more explanations.

2, 4, 1, 8, 6, 12, 16, 14, 24, 28, 32, 20, 40, 26, 48, 52, 56, 34, 64, 68, 38, 76, 80, 44, 88, 59, 96, 71, 104, 91, 121, 180, 112, 83, 136, 142, 99, 152, 1160, 166, 111, 761, 820, 219, 2198, 1020, 800, 132, 224, 118, 236, 242, 127, 254, 162, 640, 272, 145, 284, 290, 155, 230, 4310, 169, 332, 403, 323

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OFFSET

1,1

COMMENTS

A "digit-position" (DP in short) is the rank of a digit in the succession of the digits of the sequence. At DP#1 we find the digit "2" here. At DP#8 we find"1" (the 1 of 16), etc.

A term > 4 uses more than one digit when it is doubled (2*8 = 16 uses two digits, for instance, 2*50 = 100 uses three digits, etc.) The convention here says that the double of a(n) is visible in the sequence at DP#n. This means that the said double will use sometimes contiguous digits that belong to an existing term, or will use successive digits belonging to two (or more) contiguous terms. The first such example here is a(17) = 56 with 56 "saying" that at DP#56 starts 112 (112 is the double of 56); indeed, DP#56 = 1, DP#57 = 1 and DP#58 = 2 and those three digits are used by a(30) = 91 and a(31) = 121 like this: 9(1, 12)1.

LINKS

Table of n, a(n) for n=1..67.

CROSSREFS

Cf. A270671.

Sequence in context: A065266 A065260 A257794 * A372868 A091894 A127151

Adjacent sequences: A345878 A345879 A345880 * A345882 A345883 A345884

KEYWORD

base,nonn

AUTHOR

Eric Angelini and Carole Dubois, Jun 28 2021

STATUS

approved