A249494 - OEIS

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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

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OFFSET

1,2

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

Table of n, a(n) for n=1..91.

Index entries for sequences that are permutations of the natural numbers

PROG

(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<<a); a \\ highly unoptimized

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).

Sequence in context: A218452 A007731 A306590 * A047747 A007957 A194377

Adjacent sequences: A249491 A249492 A249493 * A249495 A249496 A249497

KEYWORD

nonn,base

AUTHOR

M. F. Hasler, Oct 30 2014

STATUS

approved