A284439 Sum the last digit of a(n) and the first digit of a(n+1); keep only the leftmost digit of the result. The succession of those "leftmost digits" is the succession of the digits of the sequence itself.

1, 91, 8, 2, 61, 11, 5, 6, 4, 62, 3, 31, 32, 41, 12, 111, 21, 92, 121, 13, 14, 7, 51, 15, 9, 16, 71, 17, 33, 611, 18, 81, 19, 22, 82, 112, 83, 113, 42, 34, 63, 72, 35, 43, 73, 36, 114, 64, 65, 211, 212, 115, 116, 44, 66, 45, 37, 117, 38, 23, 621, 131, 122, 631, 118, 24, 641, 123, 52, 119, 25, 511, 213, 141, 132, 133, 124

Offset

1,2

Comments

The sequence is started with a(1) a= 1 and always extended with the smallest integer not yet present and not leading to a contradiction. There are no "0" digits in the sequence as a this 0 would be the leftmost digit of a later sum -- which is impossible.

Is this a permutation of the list (A052382) of numbers with no zero digits? - N. J. A. Sloane, Mar 27 2017

Links

Jean-Marc Falcoz, Table of n, a(n) for n = 1..10001

Example

The 1st sum is 1+9, with result 10, and leftmost digit 1;
The 2nd sum is 1+8, with result 9, and leftmost digit 9;
The 3rd sum is 8+2, with result 10, and leftmost digit 1;
The 4th sum is 2+6, with result 8, and leftmost digit 8;
The 5th sum is 1+1, with result 2, and leftmost digit 2;
The 6th sum is 1+5, with result 6, and leftmost digit 6, etc.
The 6 "leftmost digits" so far are [1,9,1,8,2,6]; those are precisely the first 6 digits of the sequence.

Crossrefs

Cf. A052382.

Sequence in context: A175690 A368433 A283896 * A364664 A119656 A368238

Adjacent sequences: A284436 A284437 A284438 * A284440 A284441 A284442

Keyword

nonn,base

Author

Eric Angelini and Jean-Marc Falcoz, Mar 27 2017

Status

approved