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A160265 Each of the numbers describes the previous number, and is described by the next number. 0
1, 11, 12, 1121, 1321, 123121, 132231, 123222, 112431, 13214131, 14322141, 13423122, 12324123, 12233241, 12233241, 12233241, 12233241, 12233241, 12233241, 12233241, 12233241, 12233241, 12233241, 12233241, 12233241, 12233241, 12233241, 12233241, 12233241, 12233241 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
Starting with 1, each of the rest describes the previous number in a "digit + number_of_digits" manner. The odd-indexed digits are digits that appeared in the previous term, ordered by the first appearance. The even-indexed digits are how many times that digit appeared. [Edited by Michel Marcus, Oct 26 2021]
LINKS
MATHEMATICA
NestList[FromDigits@Flatten@Tally@IntegerDigits@#&, 1, 30] (* Giorgos Kalogeropoulos, Oct 26 2021 *)
PROG
(PARI) lista(nn) = {my(v = vector(nn)); v[1] = 1; for (n=2, nn, my(vd = digits(v[n-1]), vu = Set(vd), vw = vector(#vu), pos=0, ss=""); for (i=1, #vd, if (!setsearch(Set(vw), vd[i]), pos++; vw[pos] = vd[i]); ); for (i=1, #vw, ss = concat(ss, vw[i]); ss = concat(ss, #select(x->(x==vw[i]), vd)); ); v[n] = eval(ss); ); v; } \\ Michel Marcus, Oct 26 2021
CROSSREFS
A variant of A005150. See Index entries under "Say what you see". - N. J. A. Sloane, May 10 2009
Cf. A121808.
Sequence in context: A087304 A340204 A121808 * A007651 A022481 A156338
KEYWORD
nonn,base
AUTHOR
Adrian Lee (prof.adrian.lee(AT)gmail.com), May 07 2009
EXTENSIONS
More terms from Michel Marcus, Oct 26 2021
STATUS
approved

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Last modified April 19 19:02 EDT 2024. Contains 371798 sequences. (Running on oeis4.)