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, 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

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