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A247476

A Skolem-type sequence: each pair of two terms that start with a digit k are separated by k other terms. Lexicographically earliest permutation of positive integers with this property.

1, 2, 10, 3, 20, 4, 5, 30, 6, 7, 40, 8, 50, 9, 11, 60, 12, 70, 21, 41, 80, 22, 23, 90, 42, 24, 13, 25, 14, 15, 26, 16, 17, 27, 18, 19, 28, 100, 29, 31, 43, 200, 51, 32, 61, 44, 33, 45, 52, 53, 34, 62, 46, 35, 47, 54, 55, 36, 63, 48, 37, 49, 56, 57, 38, 64, 400

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

LINKS

Rémy Sigrist, Table of n, a(n) for n = 1..10000

E. Angelini, A Skolem-like seq with no terms repeated, SeqFan list, Nov 22 2014

Rémy Sigrist, Illustration of first terms

Rémy Sigrist, PARI program for A247476

EXAMPLE

The sequence starts 1,2,10,...: there is 1 term enclosed by 1 and 10: the term 2.

Then it goes on 1,2,10,3,20,...: there are 2 terms (10 and 3) enclosed between 2 and 20.

Then, in 1,2,10,3,20,4,5,30,... there are 3 terms (20, 4 and 5) enclosed by 3 and 30, etc.