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.

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

Offset

1,2

Comments

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

Links

Jean-Marc Falcoz, Table of n, a(n) for n = 1..16384

Formula

a(n) = A284971(n-2) for n>=3. - Alois P. Heinz, Jul 15 2023

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 Jean-Marc Falcoz, Apr 16 2018

Status

approved