cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-2 of 2 results.

A316680 The integer 1358 and its infinite continuation (when iterating the rule explained in A316650 and in the Comment section here).

Original entry on oeis.org

1358, 7915, 35917, 143617, 65281, 29677, 95710, 435010, 334624, 152104, 117004, 90004, 69235, 276910, 1107610, 6922510, 27690010, 110760010, 692250010, 2769000010, 11076000010, 69225000010, 276900000010, 1107600000010, 6922500000010, 27690000000010, 110760000000010, 692250000000010, 2769000000000010
Offset: 1

Views

Author

Eric Angelini and Jean-Marc Falcoz, Jul 10 2018

Keywords

Comments

It is conjectured, when iterating the idea explained in A316650 ("Result when n is divided by the sum of its digits and the resulting integer is concatenated with the remainder"), that all integers will end either on a fixed point (the first ones are listed in A052224) or grow forever (like 907 or 1358).

Examples

			1358/17 gives 79 with remainder 15;
7915/22 gives 359 with remainder 17;
35917/25 gives 1436 with remainder 17;
143617/22 gives 6528 remainder 1;
...
After 6922510 starts a devilish inflation "from the middle", in a ternary cycle:
6922510
27690010
110760010
692250010
2769000010
11076000010
69225000010
276900000010
1107600000010
6922500000010
27690000000010
110760000000010
692250000000010
2769000000000010
11076000000000010
69225000000000010
276900000000000010
1107600000000000010
6922500000000000010
...
We have:
2769(k zeros)10
11076(k zeros)10
69225(k zeros)10
then:
2769(k+2 zeros)10
11076(k+2 zeros)10
69225(k+2 zeros)10
then:
2769(k+4 zeros)10
11076(k+4 zeros)10
69225(k+4 zeros)10
Etc.
		

Crossrefs

Cf. A316650 (where the rule is explained).
Cf. A316679 (for an equivalent pattern produced by 907).

Programs

  • Mathematica
    NestList[FromDigits@ Flatten[IntegerDigits@ # & /@ QuotientRemainder[#, Total[IntegerDigits@ #]]] &, 1358, 28] (* Michael De Vlieger, Jul 10 2018 *)

A316678 Smallest numbers leading in n steps to a term that repeats itself, according to the rule explained in A316650 (and hereunder in the Comment section).

Original entry on oeis.org

19, 31, 13, 16, 32, 11, 23, 15, 236, 282, 341, 1047, 787, 419, 286, 626, 557, 498, 1357, 1001, 368, 1921, 917, 2077, 3319, 3457, 5090, 2294, 2144, 3501, 4485, 10661, 16753, 3092, 5252, 3475, 2102, 3572, 656, 1691, 7461, 10445, 4596, 13937, 15964, 25540, 14380
Offset: 1

Views

Author

Eric Angelini and Jean-Marc Falcoz, Jul 10 2018

Keywords

Comments

It is conjectured, when iterating the idea explained in A316650 ("Result when n is divided by the sum of its digits and the resulting integer is concatenated to the remainder"), that all integers will end either on a fixed point (the first ones are listed in A052224) or grow forever [10 is an example of a simple pattern: 10,100,1000,10000,100000,. . .]
The Crossrefs section gives two more interesting such infinite growing patterns.

Examples

			19 is the smallest integer leading to itself in 1 step because we have [19/10 = 10*1 + 9];
31 is the smallest integer ending on a fixed point in 2 steps because 31 leads to 73 [31/4 = 4*7 + 3] (step 1) and 73 to itself [73/10 = 10*7 + 3] (step 2);
13 is the smallest integer ending on a fixed point in 3 steps because 13 leads to 31 [13/4 = 4*3 + 1] (step 1) and 31 leads to 73 in 2 steps (see above);
16 is the smallest integer ending on a fixed point in 4 steps because 16 leads to 22 [16/7 = 7*2 + 2] (step 1), then 22 leads to 52 [22/4 = 4*5+2] (step 2), then 52 leads to 73 [52/7 = 7*7 + 3] (step 3) and 73 to itself [73/10 = 10*7 + 3] (step 4);
32 is the smallest integer ending on a fixed point in 5 steps [32,62,76,511,730];
11 is the smallest integer ending on a fixed point in 6 steps
  [11,51,83,76,511,730];
23 is the smallest integer ending on a fixed point in 7 steps
  [23,43,61,85,67,52,73];
Etc.
		

Crossrefs

Cf. A316650 (where the main idea is explained), A316679 (for the infinite growing pattern produced by 907) and A316680 (for the infinite growing pattern produced by 1358).

Programs

  • Mathematica
    Array[Block[{k = 1}, While[Count[#, 0] != 1 &@ Differences@ NestList[FromDigits@ Flatten[IntegerDigits@ # & /@ QuotientRemainder[#, Total[IntegerDigits@ #]]] &, k, #], k++]; k] &, 47] (* Michael De Vlieger, Jul 10 2018 *)
Showing 1-2 of 2 results.