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 A332072 The Blue Comma sequence: Differences of indices of even terms gives back the sequence; lexicographically earliest such permutation of positive integers. 0
 1, 2, 4, 3, 6, 5, 7, 9, 8, 11, 13, 10, 15, 17, 19, 21, 23, 12, 25, 27, 29, 31, 14, 33, 35, 37, 39, 41, 43, 16, 45, 47, 49, 51, 53, 55, 57, 59, 18, 61, 63, 65, 67, 69, 71, 73, 20, 75, 77, 79, 81, 83, 85, 87, 89, 91, 93, 22, 95, 97, 99, 101, 103, 105, 107, 109, 111, 113, 115, 117, 24, 119, 121, 123, 125, 127 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Eric Angelini, Yellow commas, pink, red, blue..., personal blog "Cinquante signes" on blogspot.com, May 17 2020 EXAMPLE The even terms are at indices 2, 3, 5, 9, 12, 18, 23, 30, ...; first differences give 1, 2, 4, 3, 6, 5, 7, ... = the sequence itself. PROG (PARI) upto(N)={my(a=Vec([1, 2], N), i=1, L=2); local(U=[2], nxt(e)=while(#U>1&&U[2]==U[1]+1, U=U[^1]); my(t=U[1]); until( t++%2!=e && !setsearch(U, t), ); U=setunion(U, [t]); t ); for(n=3, N, a[n]=nxt(n-L==a[i] && i++ && L=n)); a} CROSSREFS Cf. A197756 (the Yellow Comma sequence: count digits between odd terms). Sequence in context: A278511 A255552 A255551 * A330340 A328696 A053629 Adjacent sequences:  A332069 A332070 A332071 * A332073 A332074 A332075 KEYWORD nonn AUTHOR Eric Angelini and M. F. Hasler, May 19 2020 STATUS approved

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Last modified July 31 18:15 EDT 2021. Contains 346376 sequences. (Running on oeis4.)