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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. 2
 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 (list; graph; refs; listen; history; text; internal format)
 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<

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Last modified September 22 21:28 EDT 2023. Contains 365531 sequences. (Running on oeis4.)