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 1-3 of 3 results.

A281067 a(1) = 1; a(n) is the smallest natural number such that a(n) > a(n-1), and the name of a(n) in English starts with the letter a(n-1) ends with, and a(n) makes the sequence extendable.

Original entry on oeis.org

1, 8, 10, 19, 91, 801, 802, 1001, 8001, 8002, 100001, 800001, 800002, 1000000, 9000000, 9000001, 11000000, 19000000, 19000001, 80000000, 90000000, 90000001, 800000000, 900000000, 900000001, 8000000000, 9000000000, 9000000001, 11000000000, 19000000000, 19000000001, 80000000000, 90000000000, 90000000001
Offset: 1

Views

Author

Ivan N. Ianakiev, Jan 14 2017

Keywords

Comments

"a(n) makes the sequence extendable" means the name of a(n) does not end with any of the letters r, x, y and d.

Examples

			If a(5) were 90 (ninety, which ends with y), it would make the sequence finite. Therefore, a(5) has to be 91.

Crossrefs

Cf. A277971, A277972, A281068.

A282636 a(1) = 1. a(n) is the smallest natural number such that a(n) > a(n-1), the name of a(n) in (American) English ends with the letter a(n-1) starts with, and a(n) makes the sequence extendable.

Original entry on oeis.org

1, 2, 8, 9, 10, 28, 38, 88, 89, 91, 97, 107, 122, 132, 142, 152, 162, 172, 182, 192, 202, 208, 228, 238, 248, 258, 268, 278, 288, 298, 308, 328, 338, 348, 358, 368, 378, 388, 398, 808, 809, 812, 821, 823, 825, 829, 831, 833, 835, 839, 841, 843, 845, 849, 851, 853, 855, 859
Offset: 1

Views

Author

Ivan N. Ianakiev, Feb 20 2017

Keywords

Comments

"a(n) makes the sequence extendable" means the name of a(n) does not start with any of the letters f and s.

Examples

			38 is followed by 88 as 48, 58, 68 and 78 cannot make the sequence extendable.

Crossrefs

Cf. A277971, A277972, A281067, A281068, A282637.

Programs

  • Mathematica
    names = StringReplace[
   IntegerName /@ Range[1000], {"\[Hyphen]" -> "", " " -> ""}];
lst = {1}; next[n_] := next[n] =
  Module[{pos = Last[lst] + 1},
   While[
    Or[
     And[First[Characters[names[[Last[lst]]]]] !=
       Last[Characters[names[[pos]]]], pos <= Length[names]],
     MemberQ[{"f", "s"}, First[Characters[names[[pos]]]]] == True
     ],
    pos++
    ];
   AppendTo[lst, pos]
   ];
seq[n_] := Nest[next, 1, n]; seq[57]

A282637 a(1) = 1. a(n) is the smallest unlisted natural number whose name in (American) English ends with the letter a(n-1) starts with, and makes the sequence extendable.

Original entry on oeis.org

1, 2, 8, 3, 28, 38, 88, 9, 10, 98, 11, 12, 108, 22, 128, 32, 138, 82, 21, 148, 92, 13, 158, 102, 122, 132, 142, 152, 162, 172, 182, 192, 202, 168, 222, 178, 232, 188, 242, 198, 252, 208, 228, 238, 248, 258, 268, 278, 288, 298, 308, 328, 338, 348, 358, 368, 378, 388, 398, 808, 23, 828, 25, 838, 29, 848
Offset: 1

Views

Author

Ivan N. Ianakiev, Feb 20 2017

Keywords

Comments

"a(n) ... makes the sequence extendable" means the name of a(n) does not start with any of the letters f and s.

Examples

			38 is followed by 88 as 48, 58, 68 and 78 cannot make the sequence extendable.

Crossrefs

Cf. A277971, A277972, A281067, A281068, A282636.

Programs

  • Mathematica
    names = StringReplace[
   IntegerName /@ Range[1000], {"\[Hyphen]" -> "", " " -> ""}];
lst = {1}; next[n_] := next[n] =
  Module[{pos = Complement[Range[Length[names]], lst], i = 1},
   While[
    Or[
     And[
      First[Characters[names[[Last[lst]]]]] != Last[Characters[names[[pos[[i]]]]]],
      pos[[i]] <= Length[names]
      ],
     MemberQ[{"f", "s"}, First[Characters[names[[pos[[i]]]]]]] == True
     ],
    i++
    ];
   AppendTo[lst, pos[[i]]]
   ];
seq[n_] := Nest[next, 1, n]; seq[65]
Showing 1-3 of 3 results.

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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