cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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A375243 Infinite variant of A375232.

Original entry on oeis.org

0, 10, 20, 100, 30, 102, 40, 101, 203, 105, 60, 1024, 300, 107, 200, 150, 304, 1026, 80, 109, 230, 10457, 0, 120, 306, 110, 204, 1058, 303, 10279, 0, 1046, 302, 501, 0, 201, 3048, 170, 206, 1059, 330, 1042, 0, 1000, 320, 105678, 400, 210, 3000, 190, 202, 1045, 360, 1027, 800, 1001, 2034, 510, 0, 10269
Offset: 1

Views

Author

Eric Angelini and Jean-Marc Falcoz, Aug 07 2024

Keywords

Comments

Instead of stopping the sequence when no integer is available, we extend it with 0 and go on (0 being the only term allowed to be repeated whenever nothing else works). This method seems to work ad infinitum.
Around 90% of the terms are not equal to 0.
For the first 1000 terms, the largest chunk between two successive 0 is the 24-integer long serie [101101, 2630, 8015, 40044, 10122, 333330, 1907, 200222, 10456, 10200, 80008, 101110, 3204, 5107, 6660, 9012, 1400, 202000, 8051, 10276, 40400, 101111, 20223, 5109].

Examples

			The finite sequence A375232 ends with 80, 109, 230, 10457. If we extend it with a(23) = 0, we can compute a(24) = 120, a(25) = 306 then 110, 204, 1058, 303 and 10279. No more integers are available at that stage. But, again, we can extend the sequence with a(31) = 0, then a(32) = 1046 and 302, 501, 0, 201, 3048, 170, etc.
A repeated single 0 is counted as a term of the sequence.
		

Crossrefs

A376150 Define b_n(k) to be the lexicographically earliest sequence of distinct nonnegative integers with the property that two terms that contain the digit "d" are always separated by exactly "d" terms that do not contain the digit "d", in base n. a(n) is the number of terms in b_n(k).

Original entry on oeis.org

2, 4, 6, 10, 10, 18, 18, 22, 22, 30, 30, 34, 42, 42, 78, 78, 78, 78, 102, 102, 114, 114, 114, 114, 142, 142, 142, 142, 214, 214, 214, 214, 214, 214, 214, 222, 274, 274, 274, 274, 274, 354, 354, 354, 354, 354, 354, 642, 642, 642, 642, 642, 642, 642, 642
Offset: 2

Views

Author

Jake Bird, Sep 12 2024

Keywords

Comments

This process terminates only when all nonzero digits are prohibited by the restrictions in place for the next term; as b_n(2) = "10" for all n, the digit 1 is only prohibited for odd numbered terms, and as such a(n) must be even for all n. Similar logic can be applied to the digit 3 to show that for all n>3, a(n) is not divisible by 4.
A375232 is the sequence generated when n=10.

Examples

			For n = 5:
b_5(1) = 0; as this contains the digit 0, b_5(2), b_5(3) etc. must also contain a 0
b_5(2) = 10 (= 5 in decimal); must contain a 0 from b_5(1); as this contains the digit 1, b_5(4), b_5(6) etc. must also contain a 1, and all other terms must not contain a 1
b_5(3) = 20; must have 0 but not 1
b_5(4) = 100; must have 0 and 1 but not 2
b_5(5) = 30; must have 0 but not 1 or 2
b_5(6) = 102; must have 0, 1, and 2, but not 3
b_5(7) = 40; must have 0 but not 1, 2, or 3
b_5(8) = 101; must have 0 and 1 but not 2, 3, or 4
b_5(9) = 203; must have 0, 2, and 3, but not 1 or 4
b_5(10) = 110; must have 0 and 1 but not 2, 3, or 4
b_5(11) = ---; must have 0 but not 1, 2, 3, or 4 - the only number that fills this condition is 0, but 0 already appears in the sequence, so the sequence terminates after ten terms, and a(5) = 10
		

Crossrefs

Cf. A375232.
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