A117521 -id:A117521 - cp's OEIS frontend

A117816 Number of steps until the RADD sequence T(k+1) = n + R(T(k)), T(0) = 1, enters a cycle; -1 if no cycle is ever reached. (R=A004086: reverse digits).

1, 1, 1, 1, 1, 1, 1, 1, 1, -1, 1, 2, 31, 15, -1, 721, 9, 1, 6, -1, 3, 5, 28, 29, 131, 23, 1, 31, 6, -1, 1, 19, 1, 53, 4, 406, 34, 254, 8, -1, 3, 245, 1, 3, 2, 422, 42, 308, 1, -1, 2, 2, 49, 1, 1371, 13, 1, 1, 2, -1, 78, 65, 1, 809, 1575, 5, 43, 31, 2, -1, 33, 2, 21, 192, 857, 91, 1, 2, 2, -1, 2, 491, 1, 2, 1, 81, 49, 1, 2, -1, 35, 197, 72, 1, 12, 79, 1, 6004, 1, -1, 52, 10264, 9, 28, 2, 2, 1, 427, 1, -1, 1, 1, 49, 167

Offset: 1

N. J. A. Sloane, following discussions with Luc Stevens, May 04 2006

Comments following discussions with David Applegate, May 05 2006: (Start)
Certainly a(10) = -1 and probably a(n) is always -1 if n is a multiple of 10. Furthermore a(15) is almost certainly -1: T_15 has not reached a cycle in 10^7 terms (see A118532).
(End)
If n is a multiple of 10 the operation can never generate a trailing zero and so is reversible. So it loops only if it returns to the start, which is impossible. Hence a(10k) = -1. - Martin Fuller, May 12 2006
I suspect a(115) = 385592406, A117817(115) = 79560. Can someone confirm? - Martin Fuller, May 12 2006
The map f: x -> R(x)+n is injective, f(x)=f(y) <=> R(x)=R(y) <=> x=y, unless x or y only differ in trailing zeros. For n=10k, however, trailing zeros can never occur. (This also implies that the terms are of increasing length.) Thus, for n=10k, no number can occur twice in the orbit of 1 under f, i.e., a(10k)=-1. A sketch of proof for a(15)=-1 is given in A118532. As of today, no other n with a(n)=-1 seems to be known. - M. F. Hasler, May 06 2012

			T_2 enters a cycle of length 81 after 1 step.

N. J. A. Sloane and others, Sequences of RADD type, OEIS wiki.

For T_1, T_2, ..., T_16 (omitting T_9, which is uninteresting) see A117230, A117521, A118517, A117828, A117800, A118525, A118526, A118527, A117841, A118528, A118529, A118530, A118531, A118532, A118533.

Cf. A117817.

ReverseNum[n_] := FromDigits[Reverse[IntegerDigits[n]]]; maxLen=10000; Table[z=1; lst={1}; While[z=ReverseNum[z]+n; !MemberQ[lst,z] && Length[lst]T. D. Noe *)

A117816(n,L=10^5,S=1)={ for(F=0,1, my(u=Vecsmall(S)); while(L-- & #u<#u=vecsort(concat(u,Vecsmall(S=A004086(S)+n)),,8),); L || F=1; /* 1st run counts until repetition, now subtract cycle length */ F || L=1+#u); L-1}

a(21)-a(33) from Luc Stevens, May 08 2006
a(33) onwards from T. D. Noe, May 10 2006
Further terms from Martin Fuller, May 12 2006

A117831 Let S_n be the infinite sequence formed by starting with n and repeatedly reversing the digits and adding 4 to get the next term. Sequence gives number of steps for S_n to reach a cycle, or -1 if no cycle is ever reached.

Original entry on oeis.org

1, 1, 40, 7, 0, 0, 39, 6, 0, 0, 38, 5, 0, 18, 37, 3, 0, 43, 10, 0, 4, 42, 9, 4, 4, 41, 7, 0, 47, 40, 0, 8, 46, 13, 0, 8, 45, 11, 0, 7, 44, 0, 12, 50, 17, 3, 12, 49, 15, 1, 11, 48, 1, 16, 36, 3, 0, 16, 35, 1, 0, 41, 8, 2, 2, 40, 7, 2, 2, 39, 5, 0, 45, 12, 0, 6, 44, 11, 0, 6, 43, 9, 0, 49, 42, 0, 10

Offset: 1

N. J. A. Sloane, following discussions with Luc Stevens, May 03 2006

It is conjectured that S_n always reaches a cycle.

There are 22 different cycles of length 90 with 4-digit components. I guess that at most half of the numbers between 1000 and 10000 lead to the cycle of length 54 shown in A117830. - Klaus Brockhaus, May 05 2006

Robert Israel, Table of n, a(n) for n = 1..10000
N. J. A. Sloane and others, Sequences of RADD type, OEIS wiki.

S_1 is given in A117828, S_3 in A117829, S_1015 in A117807.
Records are in A118473, A118474.
Full list of sequences on this topic (1): A117230, A117521, A117800, A117816, A117817, A117827, A117828, A117829, A117830, A117831 (this sequence)
Full list of sequences on this topic (2): A117837, A117841, A118473, A118474, A118510, A118511, A118512, A118513, A118514, A118515, A118516
Full list of sequences on this topic (3): A118517-A118533, A118535

V:= Vector(10^5,-1):
f:= proc(n)
  local L, H, S, i, j,found,x,y;
  global V;
  S:= {n}: H:= n; x:= n;
  for i from 1 to 10^5 do
    if V[x] > -1 then
       for j from 1 to i-1 do V[H[j]]:= i-j+V[x] od;
       return V[n];
    fi;
    L:= convert(x,base,10);
    x:= add(L[-j]*10^(j-1),j=1..nops(L)) + 4;
    if member(x, S) then
      found:= false; y:= 0;
      V[x]:= 0;
      for j from i by -1 to 1 do
        if H[j] = x then found:= true
        elif not found then V[H[j]]:= 0
        else y:= y+1; V[H[j]]:= y;
        fi
      od;
      return V[n]
    fi;
    H:= H, x;
    S:= S union {x};
  od;
end proc:
map(f, [$1..200]); # Robert Israel, May 07 2020

Corrected and extended by Klaus Brockhaus, May 05 2006

Confirmed by N. J. A. Sloane, May 05 2006

A118514 Define sequence S_n by: initial term = n, reverse digits and add 2 to get next term. It is conjectured that S_n always reaches a cycle. Sequence gives number of steps for S_n to reach a cycle.

Original entry on oeis.org

1, 3, 0, 2, 0, 1, 0, 0, 0, 0, 0, 9, 0, 7, 10, 0, 9, 4, 0, 3, 8, 8, 8, 7, 15, 5, 5, 3, 12, 1, 11, 16, 0, 7, 0, 5, 8, 0, 7, 2, 0, 6, 6, 6, 6, 5, 13, 3, 3, 1, 10, 6, 9, 14, 0, 5, 0, 3, 6, 0, 5, 4, 0, 4, 4, 4, 4, 3, 11, 1, 1, 13, 8, 4, 7, 12, 0, 3, 0, 1, 4, 2, 3, 2, 0, 2, 2, 2, 2, 1, 9, 12, 0

Offset: 1

N. J. A. Sloane, May 06 2006

Initial cycles have length 81 or 90.
There is one cycle of length 81 (least component is 3, all components have at most three digits, cf. A117521), 22 cycles of length 90 with 4-digit components (least components are 1013 + 2*k for k = 0, ..., 21, cf. A120214) and one cycle of length 45 with 4-digit components (least component is 1057, cf. A120215). Furthermore there are 22 cycles of length 1890 (least components are 100013 + 2*k for k = 0, ..., 21, cf. A120216), one cycle of length 945 (least component is 100057, cf. A120217) and 225 cycles of length 900 (least components are 100103 + 2*k for k = 0, ..., 224, cf. A120218), all having 6-digit components. It is conjectured that there are also cycles of increasing length with 8-, 10-, 12-, ... digit components. - Klaus Brockhaus, Jun 10 2006
From Michael S. Branicky, May 11 2023: (Start)
There are 22 cycles of length 19890 (least components are 10000013 + 2*k for k = 0, ..., 21), one cycle of length 9945 (least component 10000057), 225 cycles of length 18900 (least components are 10000103 + 2*k for k = 0, ..., 224) and 2250 cycles of length 9000 (least components are 10001003 + 2*k for k = 0, ..., 2249), all having 8-digit components.
These patterns continue.  Specifically, there is one cycle of length 10^(n/2) - 55 (least component 10^(n-1) + 57), and there are 22 cycles of length 2*(10^(n/2) - 55) (least components 10^(n-1) + 13 + 2*k for k = 0, ..., 21), each for n = 4, 6, 8, 10, 12, 14, 16. (End)

Michael S. Branicky, Python program for OEIS A118514, A118515, and A118516
N. J. A. Sloane and others, Sequences of RADD type, OEIS wiki.

For records see A118515, A118516. Cf. A117831. S_1 is A117521.

S_1013 is A120214, S_1057 is A120215, S_100013 is A120216, S_100057 is A120217, S_100103 is A120218.

Python
```
# see linked program
```

A117230 Start with 1 and repeatedly reverse the digits and add 1 to get the next term.

Original entry on oeis.org

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 2, 3, 4, 5, 6, 7, 8, 9, 10, 2, 3, 4, 5, 6, 7, 8, 9, 10, 2, 3, 4, 5, 6, 7, 8, 9, 10, 2, 3, 4, 5, 6, 7, 8, 9, 10, 2, 3, 4, 5, 6, 7, 8, 9, 10, 2, 3, 4, 5, 6, 7, 8, 9, 10, 2, 3, 4, 5, 6, 7, 8, 9, 10, 2, 3, 4, 5, 6, 7, 8, 9, 10, 2, 3, 4, 5, 6, 7, 8, 9, 10, 2, 3, 4, 5, 6, 7, 8, 9, 10

Offset: 1

N. J. A. Sloane, following discussions with Luc Stevens, May 04 2006

N. J. A. Sloane and others, Sequences of RADD type, OEIS wiki.
Index entries for linear recurrences with constant coefficients, signature (0, 0, 0, 0, 0, 0, 0, 0, 1).

Cf. A117830, A117521, A117828, A117800, A117816, A117817.

read transforms; t1:=[1]; for n from 1 to 80 do t1:=[op(t1),1+digrev(t1[n])]; od:

Join[{1},LinearRecurrence[{0,0,0,0,0,0,0,0,1},{2,3,4,5,6,7,8,9,10},99]] (* Ray Chandler, Jul 18 2015 *)

a(n)=if(n>1,(n-2)%9+2,1) \\ M. F. Hasler, May 22 2014

Has period 9.

G.f.: -x*(9*x^9 +9*x^8 +8*x^7 +7*x^6 +6*x^5 +5*x^4 +4*x^3 +3*x^2 +2*x +1) / ((x -1)*(x^2 +x +1)*(x^6 +x^3 +1)). - Colin Barker, May 23 2014

Correction to the terms of the sequence (inserted missing term) Jeremy Gardiner, Jun 17 2010

A120214 Start with 1013 and repeatedly reverse the digits and add 2 to get the next term.

Original entry on oeis.org

1013, 3103, 3015, 5105, 5017, 7107, 7019, 9109, 9021, 1211, 1123, 3213, 3125, 5215, 5127, 7217, 7129, 9219, 9131, 1321, 1233, 3323, 3235, 5325, 5237, 7327, 7239, 9329, 9241, 1431, 1343, 3433, 3345, 5435, 5347, 7437, 7349, 9439, 9351, 1541, 1453, 3543

Offset: 1

Klaus Brockhaus, Jun 11 2006

Let T(S,Q) be the sequence obtained by starting with S and repeatedly reversing the digits and adding Q to get the next term. This is T(1013,2). 1013 is the first S for which T(S,2) reaches a cycle of length 90. The cycle is simply the first 90 terms, which then repeat. A full period is given in the table.

Klaus Brockhaus, Table of n, a(n) for n = 1,...,90
N. J. A. Sloane and others, Sequences of RADD type, OEIS wiki.
Index entries for linear recurrences with constant coefficients, signature (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1).

Cf. A117521, A118514, A120215, A120216, A120217, A120218.

NestList[IntegerReverse[#]+2&,1013,50] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Aug 16 2016 *)

A120216 Start with 100013 and repeatedly reverse the digits and add 2 to get the next term.

Original entry on oeis.org

100013, 310003, 300015, 510005, 500017, 710007, 700019, 910009, 900021, 120011, 110023, 320013, 310025, 520015, 510027, 720017, 710029, 920019, 910031, 130021, 120033, 330023, 320035, 530025, 520037, 730027, 720039, 930029, 920041, 140031

Offset: 1

Klaus Brockhaus, Jun 11 2006

Let T(S,Q) be the sequence obtained by starting with S and repeatedly reversing the digits and adding Q to get the next term. This is T(100013,2). 100013 is the first S for which T(S,2) reaches a cycle of length 1890. The cycle is simply the first 1890 terms, which then repeat. A full period is given in the table.

Klaus Brockhaus, Table of n, a(n) for n = 1..1890
N. J. A. Sloane and others, Sequences of RADD type, OEIS wiki.
Index entries for linear recurrences with constant coefficients, order 1890.

Cf. A117521, A118514, A120214, A120215, A120217, A120218.

NestList[FromDigits[Reverse[IntegerDigits[#]]]+2&,100013,30] (* Harvey P. Dale, Oct 03 2014 *)

A120217 Start with 100057 and repeatedly reverse the digits and add 2 to get the next term.

Original entry on oeis.org

100057, 750003, 300059, 950005, 500061, 160007, 700063, 360009, 900065, 560011, 110067, 760013, 310069, 960015, 510071, 170017, 710073, 370019, 910075, 570021, 120077, 770023, 320079, 970025, 520081, 180027, 720083, 380029, 920085, 580031

Offset: 1

Klaus Brockhaus, Jun 11 2006

Let T(S,Q) be the sequence obtained by starting with S and repeatedly reversing the digits and adding Q to get the next term. This is T(100057,2). 100057 is the first S for which T(S,2) reaches a cycle of length 945. The cycle is simply the first 945 terms, which then repeat. A full period is given in the table.

Klaus Brockhaus, Table of n, a(n) for n = 1,...,945
N. J. A. Sloane and others, Sequences of RADD type, OEIS wiki.
Index entries for linear recurrences with constant coefficients, order 945.

Cf. A117521, A118514, A120214, A120215, A120216, A120218.

A120218 Start with 100103 and repeatedly reverse the digits and add 2 to get the next term.

Original entry on oeis.org

100103, 301003, 300105, 501005, 500107, 701007, 700109, 901009, 900111, 111011, 110113, 311013, 310115, 511015, 510117, 711017, 710119, 911019, 910121, 121021, 120123, 321023, 320125, 521025, 520127, 721027, 720129, 921029, 920131, 131031

Offset: 1

Klaus Brockhaus, Jun 11 2006

Let T(S,Q) be the sequence obtained by starting with S and repeatedly reversing the digits and adding Q to get the next term. This is T(100103,2). 100103 is the first S for which T(S,2) reaches a cycle of length 900. The cycle is simply the first 900 terms, which then repeat. A full period is given in the table.

Klaus Brockhaus, Table of n, a(n) for n = 1..900
N. J. A. Sloane and others, Sequences of RADD type, OEIS wiki.
Index entries for linear recurrences with constant coefficients, order 900.

Cf. A117521, A118514, A120214, A120215, A120216, A120217.

NestList[FromDigits[Reverse[IntegerDigits[#]]]+2&,100103,30] (* Harvey P. Dale, Aug 14 2012 *)

A120215 Start with 1057 and repeatedly reverse the digits and add 2 to get the next term.

Original entry on oeis.org

1057, 7503, 3059, 9505, 5061, 1607, 7063, 3609, 9065, 5611, 1167, 7613, 3169, 9615, 5171, 1717, 7173, 3719, 9175, 5721, 1277, 7723, 3279, 9725, 5281, 1827, 7283, 3829, 9285, 5831, 1387, 7833, 3389, 9835, 5391, 1937, 7393, 3939, 9395, 5941, 1497, 7943, 3499, 9945, 5501

Offset: 1

Klaus Brockhaus, Jun 11 2006

Let T(S,Q) be the sequence obtained by starting with S and repeatedly reversing the digits and adding Q to get the next term. This is T(1057,2). 1057 is the first S for which T(S,2) reaches a cycle of length 45. The cycle is simply the first 45 terms, which then repeat. A full period is shown.

N. J. A. Sloane and others, Sequences of RADD type, OEIS wiki.
Index entries for linear recurrences with constant coefficients, signature (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1).

Cf. A117521, A118514, A120214, A120216, A120217, A120218.

NestList[IntegerReverse[#]+2&,1057,50] (* Harvey P. Dale, Jan 25 2021 *)

a(n) = a(n-45). - Boštjan Gec, Sep 21 2023

A118516 Where records occur in A118514.

Original entry on oeis.org

1, 2, 12, 15, 25, 32, 102, 105, 111, 295, 392, 1002, 1918, 2187, 5812, 10009, 10011, 29995, 39992, 100002, 199918, 219987, 589912, 1000009, 1000011, 2999995, 3999992, 10000002, 19999918, 21999987, 58999912, 100000009

Offset: 1

N. J. A. Sloane, May 06 2006

All terms so far enter the cycle of length 81, cf. A117521. - Klaus Brockhaus, Jun 12 2006

Rémy Sigrist, C program
N. J. A. Sloane and others, Sequences of RADD type, OEIS wiki.

Cf. A118514, A118515.

C
```
See Links section.
```
Python
```
# See linked program in A118514.
```

a(10) to a(25) from Klaus Brockhaus, Jun 12 2006

a(26) to a(32) from Rémy Sigrist, Aug 13 2022

cp's OEIS Frontend

A117816 Number of steps until the RADD sequence T(k+1) = n + R(T(k)), T(0) = 1, enters a cycle; -1 if no cycle is ever reached. (R=A004086: reverse digits).

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A117831 Let S_n be the infinite sequence formed by starting with n and repeatedly reversing the digits and adding 4 to get the next term. Sequence gives number of steps for S_n to reach a cycle, or -1 if no cycle is ever reached.

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A118514 Define sequence S_n by: initial term = n, reverse digits and add 2 to get next term. It is conjectured that S_n always reaches a cycle. Sequence gives number of steps for S_n to reach a cycle.

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A117230 Start with 1 and repeatedly reverse the digits and add 1 to get the next term.

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A120214 Start with 1013 and repeatedly reverse the digits and add 2 to get the next term.

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A120216 Start with 100013 and repeatedly reverse the digits and add 2 to get the next term.

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A120217 Start with 100057 and repeatedly reverse the digits and add 2 to get the next term.

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A120218 Start with 100103 and repeatedly reverse the digits and add 2 to get the next term.

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A120215 Start with 1057 and repeatedly reverse the digits and add 2 to get the next term.

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