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.

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'

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

A261787 a(n) is the smallest nonzero number that is not a substring of n in ternary representation.

Original entry on oeis.org

1, 2, 1, 2, 2, 3, 1, 3, 1, 2, 2, 4, 2, 2, 3, 3, 3, 3, 1, 3, 1, 4, 3, 3, 1, 3, 1, 2, 2, 4, 2, 2, 4, 4, 4, 4, 2, 2, 5, 2, 2, 3, 3, 3, 3, 3, 3, 3, 4, 3, 3, 3, 3, 3, 1, 3, 1, 4, 3, 3, 1, 3, 1, 4, 4, 4, 5, 3, 3, 3, 3, 3, 1, 3, 1, 4, 3, 3, 1, 3, 1, 2, 2, 4, 2, 2
Offset: 0

Views

Author

Reinhard Zumkeller, Sep 01 2015

Keywords

Links

Crossrefs

Cf. A007089, A030341, A261789, A261786, A261461, A261794.

Programs

  • Haskell
    import Data.List (isInfixOf)
a261787 x = f $ tail a030341_tabf where
   f (cs:css) = if isInfixOf cs (a030341_row x)
                   then f css else foldr (\d v -> 3 * v + d) 0 cs
  • PARI
    ts(n) = Str(fromdigits(digits(n, 3)));
a(n) = my(s=ts(n), k=1); while (#strsplit(s, ts(k)) != 1, k++); k; \\ Michel Marcus, Feb 05 2022

Formula

A261789(n) = a(A261786(n)).

A261793 Successively add the smallest number that is not a substring in decimal representation.

Original entry on oeis.org

1, 3, 4, 5, 6, 7, 8, 9, 10, 12, 15, 17, 19, 21, 24, 25, 26, 27, 28, 29, 30, 31, 33, 34, 35, 36, 37, 38, 39, 40, 41, 43, 44, 45, 46, 47, 48, 49, 50, 51, 53, 54, 55, 56, 57, 58, 59, 60, 61, 63, 64, 65, 66, 67, 68, 69, 70, 71, 73, 74, 75, 76, 77, 78, 79, 80, 81
Offset: 1

Views

Author

Reinhard Zumkeller, Sep 01 2015

Keywords

Links

Crossrefs

Cf. A031298, A261794, A261795 (first differences), A261806, A260273, A261786

Programs

  • Haskell
    a261793 n = a261793_list !! (n-1)
a261793_list = iterate (\x -> x + a261794 x) 1
Showing 1-4 of 4 results.

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