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 A200780 a(n) = number of i in the range 1 <= i <= n such that b(i)=b(n), where b is the sequence A181391 taken with offset 1. 1
 1, 2, 1, 3, 1, 4, 2, 3, 2, 1, 5, 1, 6, 4, 2, 2, 1, 7, 3, 1, 8, 2, 5, 1, 9, 2, 2, 3, 3, 1, 10, 4, 4, 4, 1, 11, 5, 5, 6, 6, 1, 12, 5, 1, 13, 6, 1, 14, 7, 8, 3, 1, 15, 7, 2, 1, 16, 3, 1, 17, 9, 2, 1, 18, 4, 1, 19, 10, 2, 11, 7, 1, 20, 6, 2, 12, 7, 13, 8, 2, 1, 21, 3, 1, 22, 14, 3, 3, 1, 23, 8, 1, 24, 15, 4, 5, 4 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Equivalently, this is the ORDINAL transform of Van Eck's sequence A181391. - N. J. A. Sloane, Apr 09 2020 LINKS Rémy Sigrist, Table of n, a(n) for n = 1..10000 Rémy Sigrist, C++ program for A200780 MAPLE # The ORDINAL transform of a sequence a[0], a[1], a[2], ... is the sequence b[0], b[1], b[2], ... where b[n] is the number of times a[n] has occurred in [a[0], ..., a[n]]. ORDINAL:=proc(a) local b, t1, tlist, clist, n, t, nt; if whattype(a) <> list then RETURN([]); fi: t1:=nops(a); tlist:=[]; clist:=Array(1..t1, 0); b:=[]; nt:=0; for n from 1 to t1 do t:=a[n]; if member(t, tlist, 'p') then clist[p] := clist[p]+1; b:=[op(b), clist[p]]; else nt:=nt+1; tlist:=[op(tlist), t]; clist[nt]:=1; b:=[op(b), 1]; fi; od: b; end: # N. J. A. Sloane, Apr 09 2020 See also A200779. PROG (C++) See Links section. CROSSREFS Cf. A181391. Sequence in context: A108466 A211110 A325828 * A338899 A362071 A194943 Adjacent sequences: A200777 A200778 A200779 * A200781 A200782 A200783 KEYWORD nonn AUTHOR N. J. A. Sloane, Nov 22 2011 STATUS approved

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Last modified April 16 02:39 EDT 2024. Contains 371696 sequences. (Running on oeis4.)