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 1-4 of 4 results.

A261786 Successively add the smallest ternary number that is not a substring.

Original entry on oeis.org

1, 3, 5, 8, 9, 11, 15, 18, 19, 22, 25, 28, 30, 32, 36, 38, 43, 46, 49, 52, 55, 58, 61, 64, 68, 71, 74, 75, 79, 82, 84, 86, 90, 92, 96, 100, 104, 108, 110, 115, 120, 122, 125, 128, 131, 134, 137, 140, 143, 146, 150, 153, 156, 160, 163, 166, 169, 172, 176, 179
Offset: 1

Views

Author

Reinhard Zumkeller, Sep 01 2015

Keywords

Links

Crossrefs

Cf. A007089, A261787, A261789 (first differences), A261788, A260273, A261793.

Programs

  • Haskell
    a261786 n = a261786_list !! (n-1)
a261786_list = iterate (\x -> x + a261787 x) 1
  • PARI
    ts(n) = Str(fromdigits(digits(n, 3))); \\ A007089
f(n) = my(s=ts(n), k=1); while (#strsplit(s, ts(k)) != 1, k++); k; \\ A261787
lista(nn) = my(v = vector(nn)); v[1] = 1; for (n=2, nn, v[n] = v[n-1] + f(v[n-1]);); v; \\ Michel Marcus, Feb 06 2022

A261789 First differences of A261786.

Original entry on oeis.org

2, 2, 3, 1, 2, 4, 3, 1, 3, 3, 3, 2, 2, 4, 2, 5, 3, 3, 3, 3, 3, 3, 3, 4, 3, 3, 1, 4, 3, 2, 2, 4, 2, 4, 4, 4, 4, 2, 5, 5, 2, 3, 3, 3, 3, 3, 3, 3, 3, 4, 3, 3, 4, 3, 3, 3, 3, 4, 3, 3, 1, 4, 3, 4, 4, 5, 3, 3, 3, 3, 3, 1, 4, 3, 4, 3, 3, 1, 4, 3, 2, 2, 4, 2, 4, 4
Offset: 1

Views

Author

Reinhard Zumkeller, Sep 01 2015

Keywords

Comments

a(n) = A261787(A261786(n)).

Links

Crossrefs

Cf. A261645, A261461, A261786, A261018, A261795.

Programs

  • Haskell
    a261789 n = a261789_list !! (n-1)
a261789_list = zipWith (-) (tail a261786_list') a261786_list'

A261794 a(n) is the smallest nonzero number that is not a substring of n in decimal representation.

Original entry on oeis.org

1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 3, 2, 2, 2, 2, 2, 2, 2, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1
Offset: 0

Views

Author

Reinhard Zumkeller, Sep 01 2015

Keywords

Comments

A261795(n) = a(A261793(n)).

Links

Crossrefs

Cf. A007089, A031298, A261795, A261793, A261461, A261787.

Programs

  • Haskell
    import Data.List (isInfixOf)
a261794 x = f $ tail a031298_tabf where
   f (cs:css) = if isInfixOf cs (a031298_row x)
                   then f css else foldr (\d v -> 10 * v + d) 0 cs

Extensions

Name corrected by Álvar Ibeas, Sep 08 2020

A261788 a(n) is the smallest k such that A261786(k) >= 3^n.

Original entry on oeis.org

1, 2, 5, 12, 30, 81, 224, 626, 1747, 4909, 13811, 38934, 109889, 310666, 880125, 2500221, 7125406, 20376598, 58472481, 168349612, 486198698, 1408140693, 4088769215, 11899761717, 34703682407
Offset: 0

Views

Author

Reinhard Zumkeller, Sep 01 2015

Keywords

Crossrefs

Cf. A000244, A261396, A261786, A261806.

Programs

  • Haskell
    a261788 n = a261788_list !! (n-1)
a261788_list = f 1 1 a261786_list' where
   f z k (x:xs) | x >= z    = k : f (3 * z) (k + 1) xs
                | otherwise = f z (k + 1) xs
  • PARI
    ts(n) = Str(fromdigits(digits(n, 3))); \\ A007089
f(n) = my(s=ts(n), k=1); while (#strsplit(s, ts(k)) != 1, k++); k; \\ A261787
lista(nn) = my(last=1, k=0, p=3^k); for (n=1, nn, if (last >= p, print1(n, ", "); k++; p = 3^k); last += f(last);); \\ Michel Marcus, Feb 06 2022

Extensions

a(11)-a(20) from Michel Marcus, Feb 06 2022
a(21)-a(24) from Jinyuan Wang, Dec 13 2024
Showing 1-4 of 4 results.

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