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 A080427 a(1)=1 and, for n>1, a(n) is the smallest positive integer such that the absolute difference |a(n)-a(n-1)| has not occurred previously. 2
 1, 1, 2, 4, 1, 5, 10, 1, 7, 14, 1, 9, 19, 1, 12, 24, 1, 15, 30, 1, 17, 34, 1, 20, 40, 1, 22, 44, 1, 25, 50, 1, 27, 54, 1, 29, 59, 1, 32, 64, 1, 35, 70, 1, 37, 74, 1, 39, 79, 1, 42, 84, 1, 45, 90, 1, 47, 94, 1, 49, 99, 1, 52, 104, 1, 55, 110, 1, 57, 114, 1, 60, 120, 1, 62, 124, 1, 65, 130 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS It appears (1) that a(3n+2)=1 for n=1,2,3,... and (2) that the sequence {a(3n+3)-a(3n)}={3,2,2,3,3,2,3,2,3,2,2,3,3,2,2,3,3,2,...} consists only of 2's and 3's and that the sequence of the lengths of runs of consecutive 3's in {a(3n+3)-a(3n)} is given by {1,2,1,1,2,2,2,1,...}=A026465. LINKS Rémy Sigrist, Table of n, a(n) for n = 1..10000 FORMULA It appears that abs(a(n+2)-a(n+1)) = A101544(n) for any n > 0. - Rémy Sigrist, Apr 12 2020 PROG (PARI) { my(s=0, v=1, d); for (n=1, 79, print1 (v, ", "); for (w=1, oo, if (!bittest(s, d=abs(v-w)), s+=2^d; v=w; break))) } \\ Rémy Sigrist, Apr 12 2020 CROSSREFS Cf. A026465, A067992, A101544. Sequence in context: A308437 A201283 A283739 * A118906 A085059 A336164 Adjacent sequences:  A080424 A080425 A080426 * A080428 A080429 A080430 KEYWORD nonn AUTHOR John W. Layman, Feb 19 2003 STATUS approved

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Last modified September 29 16:13 EDT 2020. Contains 337432 sequences. (Running on oeis4.)