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A275218 Numbers in 2-cycles of RATS sequences. 0
78, 117, 156, 288, 11127, 11667, 23388, 27888, 111177, 228888, 111111777, 222888888, 1111122267, 3333337788, 111111117777, 222288888888, 111111111177777, 222228888888888, 111111111111777777, 222222888888888888 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Numbers n such that A036839(A036839(n)) = n.
Subset of A161596.
Contains A002275(3*k) + 6*A002275(k) and 2*A002275(3*k)+6*A002275(2*k) for all k>0.
In particular, this sequence and A161596 are infinite.
Do all sufficiently large members of the sequence have the form A002275(3*k) + 6*A002275(k) or 2*A002275(3*k)+6*A002275(2*k)?
LINKS
EXAMPLE
78 is in the sequence because A036839(78) = 156 and A036839(156) = 78.
MAPLE
rev:= proc(n) local t, L;
L:= convert(n, base, 10);
add(10^j*L[-1-j], j=0..nops(L)-1)
end proc:
sord:= proc(n) local L, t;
L:= sort(convert(n, base, 10), `>`);
add(10^j*L[1+j], j=0..nops(L)-1)
end proc:
rats:= proc(n) option remember; sord(n + rev(n)) end proc:
Res:= NULL:
for d from 1 to 15 do
for x1 from 0 to d do
for x2 from 0 to d-x1 do
for x3 from 0 to d-x1-x2 do
for x4 from 0 to d-x1-x2-x3 do
for x5 from 0 to d-x1-x2-x3-x4 do
for x6 from 0 to d-x1-x2-x3-x4-x5 do
for x7 from 0 to d-x1-x2-x3-x4-x5-x6 do
for x8 from 0 to d-x1-x2-x3-x4-x5-x6-x7 do
x9:= d-x1-x2-x3-x4-x5-x6-x7-x8;
L:= [1$x1, 2$x2, 3$x3, 4$x4, 5$x5, 6$x6, 7$x7, 8$x8, 9$x9];
x:= add(L[-i]*10^(i-1), i=1..d);
if rats(rats(x)) = x then Res:= Res, x fi
od od od od od od od od od:
sort([Res]);
CROSSREFS
Sequence in context: A157355 A224666 A161596 * A260364 A185077 A042945
KEYWORD
nonn,base
AUTHOR
Robert Israel, Jul 20 2016
STATUS
approved

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Last modified March 28 08:22 EDT 2024. Contains 371236 sequences. (Running on oeis4.)