A167450 Smallest sequence which lists the position of digits "8" in the sequence.

2, 8, 9, 10, 11, 88, 880, 900, 901, 902, 903, 904, 905, 906, 907, 909, 910, 911, 912, 913, 914, 915, 916, 917, 919, 920, 921, 922, 923, 924, 925, 926, 8000, 9000, 9001, 9002, 9003, 9004, 9005, 9006, 9007, 9009, 9010, 9011, 9012, 9013, 9014, 9015, 9016, 9017

Offset

1,1

Comments

The lexicographically earliest sequence such that a(1),a(2),a(3),... is the (increasing) list of the positions of digits "8" in the string obtained by concatenating all these terms, written in base 10.

Links

Table of n, a(n) for n=1..50.

Example

We cannot have a(1)=1 (since then there's no "8" in the first place), but a(1)=2 is possible.
This implies that a(2) must start with a digit "8", so a(2)=8 is the smallest possible choice.
This allows us to go on with a(3)=9, a(4)=10, a(5)=11, but then must be follow 4 digits "8" (the 8th through 11th digit of the sequence), so a(6)=88 and a(7)=880 are the smallest possible choices.
Then the reasoning continues in analogy with A167452-A167457.

Prog

(PARI) concat([ [2, 8, 9, 10, 11, 88, 880], vector((88-11-1)\3, i, 900-(i<=8)+i+(i>=18)), [8000], select(x->x%10-8 & x\10%10-8, vector((880-88)\4, i, 9000-1+i)) ])

Crossrefs

Cf. A098645, A167519, A167520, A167451 - A167457.

Sequence in context: A001560 A175463 A356061 * A050569 A352698 A318175

Adjacent sequences: A167447 A167448 A167449 * A167451 A167452 A167453

Keyword

base,nonn

Author

M. F. Hasler, Nov 19 2009

Status

approved