A333470 Lexicographically earliest sequence of distinct positive terms such that a(n) is the number of commas that a(n) has to step over (to the right) to be met by an odd term. This odd term might not be the closest odd term to a(n).

1, 3, 2, 4, 5, 6, 7, 9, 8, 11, 10, 13, 12, 15, 14, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 33, 32, 35, 34, 37, 36, 39, 38, 41, 40, 43, 42, 45, 44, 47, 46, 49, 48, 51, 50, 53, 52, 55, 54, 57, 56, 59, 58, 61, 60, 63, 62, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80

Offset

1,2

Links

Dominic McCarty, Table of n, a(n) for n = 1..10000

Formula

a(n) = n for n in A053738. Otherwise, a(n) = n+1 for even n and a(n) = n-1 for odd n. - Dominic McCarty, Mar 12 2025

Example

a(1) = 1 steps over 1 comma to be met by the odd term 3;
a(2) = 3 steps over 3 commas to be met by the odd term 5;
a(3) = 2 steps over 2 commas to be met by the same odd term 5;
a(4) = 4 steps over 4 commas to be met by the odd term 9 (the odd term 5 is closer, but this is not the point);
a(5) = 5 steps over 5 commas to be met by the odd term 11 (again, the odd terms 7 and 9 are closer, but we don't care); etc.

Prog

(Python) def a(n): return n if len(bin(n))%2 else n-1 if n%2 else n+1 # Dominic McCarty, Mar 12 2025

Crossrefs

Sequence in context: A359663 A171086 A333324 * A096135 A092829 A081943

Adjacent sequences: A333467 A333468 A333469 * A333471 A333472 A333473

Keyword

base,nonn

Author

Eric Angelini and Carole Dubois, Mar 23 2020

Status

approved