A249494 Lexicographically earliest permutation of the positive integers such that the parity of the first digit of a(n+1) equals that of a(n)'s last digit.

1, 3, 5, 7, 9, 10, 2, 4, 6, 8, 20, 21, 11, 12, 22, 23, 13, 14, 24, 25, 15, 16, 26, 27, 17, 18, 28, 29, 19, 30, 40, 41, 31, 32, 42, 43, 33, 34, 44, 45, 35, 36, 46, 47, 37, 38, 48, 49, 39, 50, 60, 61, 51, 52, 62, 63, 53, 54, 64, 65, 55, 56, 66, 67, 57, 58, 68, 69, 59, 70, 80, 81, 71, 72, 82, 83, 73, 74, 84, 85, 75, 76, 86, 87, 77, 78, 88, 89, 79, 90, 200

Offset: 1

Author

M. F. Hasler, Oct 30 2014

Keywords

• nonn
• base

Comments

See A249506 for the inverse permutation.

See A249278 (and inverse A249279) for the variant based on nonnegative integers. A162501 is a variant based not on parity but on equality.

Links

• Index entries for sequences that are permutations of the natural numbers

Crossrefs

Cf. A249506 (inverse permutation), A249278 (variant starting with 0), A249279 (inverse thereof), A162501 (variant based on equality of digits).

Cf. A000030 (initial digit), A010879 (final digit of n).

Programs

PARI

a(n,a=1,u=0)=for(n=1,n,for(k=1,9e9, !bittest(u,k)&& k\10^(#Str(k)-1)==Mod(a,2)&& !print1(a=k",")&& break);u+=1<