

A302938


Lexicographically first sequence of distinct terms such that the sum of any two terms is not a term of the sequence, and the sum of any two digits is not a digit of the sequence.


2



1, 2, 4, 7, 44, 47, 74, 77, 444, 447, 474, 477, 744, 747, 774, 777, 4444, 4447, 4474, 4477, 4744, 4747, 4774, 4777, 7444, 7447, 7474, 7477, 7744, 7747, 7774, 7777, 44444, 44447, 44474, 44477, 44744, 44747, 44774, 44777, 47444, 47447, 47474, 47477, 47744, 47747, 47774, 47777, 74444, 74447
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OFFSET

1,2


COMMENTS

The full sequence uses digits 4 and 7 only, except for a(1) = 1 and a(2) = 2.


LINKS

JeanMarc Falcoz, Table of n, a(n) for n = 1..16384


EXAMPLE

1 + 2 = 3 and there is no term or digit 3 in the sequence;
1 + 4 = 5 and there is no term or digit 5 in the sequence;
1 + 7 = 8 and there is no term or digit 8 in the sequence;
2 + 4 = 6 and there is no term or digit 6 in the sequence;
2 + 7 = 9 and there is no term or digit 9 in the sequence;
4 + 4 = 8 and there is no term or digit 8 in the sequence;
4 + 7 = 11 and there is no term 11 in the sequence;
7 + 7 = 14 and there is no term 14 in the sequence;
etc.


CROSSREFS

Cf. A302940 where the word “sum” is replaced by “product”.
Cf. A014261 which shares the same property (numbers that contain odd digits only).
Cf. A284971.
Sequence in context: A004577 A285940 A211186 * A076719 A103009 A174393
Adjacent sequences: A302935 A302936 A302937 * A302939 A302940 A302941


KEYWORD

nonn,base


AUTHOR

Eric Angelini and JeanMarc Falcoz, Apr 16 2018


STATUS

approved



