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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 Table of n, a(n) for n=1..20. 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 Cf. A002275, A036839, A161596. Sequence in context: A157355 A224666 A161596 * A260364 A185077 A042945 Adjacent sequences: A275215 A275216 A275217 * A275219 A275220 A275221 KEYWORD nonn,base AUTHOR Robert Israel, Jul 20 2016 STATUS approved

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Last modified September 22 01:06 EDT 2023. Contains 365503 sequences. (Running on oeis4.)