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.

Previous Showing 11-18 of 18 results.

A213714 Inverse function for injection A005187.

Original entry on oeis.org

0, 1, 0, 2, 3, 0, 0, 4, 5, 0, 6, 7, 0, 0, 0, 8, 9, 0, 10, 11, 0, 0, 12, 13, 0, 14, 15, 0, 0, 0, 0, 16, 17, 0, 18, 19, 0, 0, 20, 21, 0, 22, 23, 0, 0, 0, 24, 25, 0, 26, 27, 0, 0, 28, 29, 0, 30, 31, 0, 0, 0, 0, 0, 32, 33, 0, 34, 35, 0, 0, 36, 37, 0, 38, 39, 0, 0, 0, 40, 41, 0, 42, 43, 0, 0, 44, 45, 0, 46, 47, 0
Offset: 0

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Author

Antti Karttunen, Oct 26 2012

Keywords

Comments

a(0)=0; thereafter if n occurs as a term of A005187, a(n)=its position in A005187, otherwise zero. This works as an "inverse" function for A005187 in a sense that a(A005187(n)) = n for all n.
a(n)*A234017(n) = 0 for all n.

Crossrefs

Can be used when computing A213715, A213723, A213724, A233275, A233277. Cf. A005187, A046699, A079559, A234017, A230414.

Programs

  • Haskell
    import Data.List (genericIndex)
    a213714 n = genericIndex a213714_list n
    a213714_list = f [0..] a005187_list 0 where
       f (x:xs) ys'@(y:ys) i | x == y    = i : f xs ys (i+1)
                             | otherwise = 0 : f xs ys' i
    -- Reinhard Zumkeller, May 01 2015
    
  • Python
    from sympy import factorial
    def a046699(n):
        if n<3: return 1
        s=1
        while factorial(2*s)%(2**(n - 1))>0: s+=1
        return s
    def a053644(n): return 0 if n==0 else 2**(len(bin(n)[2:]) - 1)
    def a043545(n):
        x=bin(n)[2:]
        return int(max(x)) - int(min(x))
    def a079559(n): return 1 if n==0 else a043545(n + 1)*a079559(n + 1 - a053644(n + 1))
    def a(n): return 0 if n==0 else a079559(n)*(a046699(n + 2) - 1) # Indranil Ghosh, Jun 11 2017

Formula

a(0)=0, for n>0, a(n) = A079559(n) * (A046699(n+2)-1) [With A046699's October 2012 starting offset. Incorrect indexing shown in this formula corrected by Antti Karttunen, Dec 18 2013]

A233275 Permutation of nonnegative integers obtained by entangling complementary pair A005187 & A055938 with even and odd numbers.

Original entry on oeis.org

0, 1, 3, 2, 6, 7, 5, 4, 12, 13, 14, 10, 15, 11, 9, 8, 24, 25, 26, 28, 27, 29, 20, 30, 21, 22, 18, 31, 23, 19, 17, 16, 48, 49, 50, 52, 51, 53, 56, 54, 57, 58, 40, 55, 59, 41, 60, 42, 61, 44, 36, 43, 45, 62, 46, 37, 38, 34, 63, 47, 39, 35, 33, 32, 96, 97, 98, 100
Offset: 0

Views

Author

Antti Karttunen, Dec 18 2013

Keywords

Comments

It seems that for all n, a(A000079(n)) = A003945(n).

Crossrefs

Inverse permutation: A233276.
Similarly constructed permutation pairs: A135141/A227413, A232751/A232752, A233277/A233278, A233279/A233280, A003188/A006068.

Formula

a(0)=0, a(1)=1, and thereafter, if A079559(n)=1, a(n) = 2*a(A213714(n)-1), else a(n) = 1+(2*a(A234017(n))).
a(n) = A054429(A233277(n)). [Follows from the definitions of these sequences]

A233277 Permutation of nonnegative integers obtained by entangling complementary pair A005187 & A055938 with odd and even numbers.

Original entry on oeis.org

0, 1, 2, 3, 5, 4, 6, 7, 11, 10, 9, 13, 8, 12, 14, 15, 23, 22, 21, 19, 20, 18, 27, 17, 26, 25, 29, 16, 24, 28, 30, 31, 47, 46, 45, 43, 44, 42, 39, 41, 38, 37, 55, 40, 36, 54, 35, 53, 34, 51, 59, 52, 50, 33, 49, 58, 57, 61, 32, 48, 56, 60, 62, 63, 95, 94, 93, 91
Offset: 0

Views

Author

Antti Karttunen, Dec 18 2013

Keywords

Crossrefs

Inverse permutation: A233278.
Similarly constructed permutation pairs: A135141/A227413, A232751/A232752, A233275/A233276, A233279/A233280, A003188/A006068.

Formula

a(0)=0, a(1)=1, and thereafter, if A079559(n)=0, a(n) = 2*a(A234017(n)), else a(n) = 1+(2*a(A213714(n)-1)).
a(n) = A054429(A233275(n)). [Follows from the definitions of these sequences]

A255560 One-based row index of n in array A255555.

Original entry on oeis.org

1, 2, 1, 2, 3, 4, 1, 2, 5, 3, 4, 6, 7, 8, 1, 2, 9, 5, 3, 10, 11, 4, 6, 12, 7, 8, 13, 14, 15, 16, 1, 2, 17, 9, 5, 18, 19, 3, 10, 20, 11, 4, 21, 22, 23, 6, 12, 24, 7, 8, 25, 26, 13, 14, 27, 15, 16, 28, 29, 30, 31, 32, 1, 2, 33, 17, 9, 34, 35, 5, 18, 36, 19, 3, 37, 38, 39, 10, 20, 40, 11, 4, 41, 42, 21, 22, 43, 23, 6
Offset: 1

Views

Author

Antti Karttunen, Apr 14 2015

Keywords

Comments

Equally: One-based column index of n in array A255557.

Crossrefs

Cf. also A255559 (corresponding column index).

Formula

a(1) = 1; for n > 1, if A213714(n) = 0 [i.e., if n is one of the terms of A055938], then a(n) = 1+A234017(n), otherwise a(n) = a(A213714(n)-1).
In other words, a(1) = 1, and for n > 1, if n = A055938(k) for some k, then a(n) = k+1, otherwise it must be that n = A005187(h) for some h, in which case a(n) = a(h-1).

A256990 One-based row index of n in array A256995.

Original entry on oeis.org

0, 1, 1, 1, 2, 3, 1, 2, 4, 3, 1, 5, 6, 7, 2, 4, 8, 3, 1, 9, 10, 5, 6, 11, 7, 2, 12, 13, 14, 15, 4, 8, 16, 3, 1, 17, 18, 9, 10, 19, 5, 6, 20, 21, 22, 11, 7, 23, 2, 12, 24, 25, 13, 14, 26, 15, 4, 27, 28, 29, 30, 31, 8, 16, 32, 3, 1, 33, 34, 17, 18, 35, 9, 10, 36, 37, 38, 19, 5, 39, 6, 20, 40, 41, 21, 22, 42, 11, 7
Offset: 1

Views

Author

Antti Karttunen, Apr 14 2015

Keywords

Comments

Also one-based column index for array A256997.
a(1) = 0 by convention, as 1 is outside of the actual arrays A256995 & A256997.

Crossrefs

Cf. A256989 (corresponding column index), A255560.

Formula

a(1) = 0; for n > 1, if A213714(n) = 0 [i.e., if n is one of the terms of A055938], then a(n) = A234017(n), otherwise a(n) = a(A213714(n)).
In other words, a(1) = 0, and for n > 1, if n = A055938(k) for some k, then a(n) = k, otherwise it must be that n = A005187(h) for some h, in which case a(n) = a(h).

A234016 Partial sums of the characteristic function of A055938.

Original entry on oeis.org

0, 0, 1, 1, 1, 2, 3, 3, 3, 4, 4, 4, 5, 6, 7, 7, 7, 8, 8, 8, 9, 10, 10, 10, 11, 11, 11, 12, 13, 14, 15, 15, 15, 16, 16, 16, 17, 18, 18, 18, 19, 19, 19, 20, 21, 22, 22, 22, 23, 23, 23, 24, 25, 25, 25, 26, 26, 26, 27, 28, 29, 30, 31, 31, 31, 32, 32, 32, 33, 34
Offset: 0

Views

Author

Antti Karttunen, Dec 18 2013

Keywords

Comments

Also: a(0) = a(1) = 0, and thereafter, a(n) = the largest k such that A055938(k) <= n.
Conjecture: partial sums of A308187 (i.e, A308187 is the characteristic function of A055938). - Sean A. Irvine, Jul 16 2022

Crossrefs

Programs

  • Python
    from sympy import factorial
    def a046699(n):
        if n<3: return 1
        s=1
        while factorial(2*s)%(2**(n - 1)): s+=1
        return s
    def a(n): return n - (a046699(n + 2) - 1)
    print([a(n) for n in range(101)]) # Indranil Ghosh, Jun 11 2017

Formula

If n < 2, a(n)=0, otherwise a(n) = a(n-1) + (1-A079559(n)).
a(n) = n - (A046699(n+2)-1) [With A046699's October 2012 starting offset].

A276344 Permutation of natural numbers: a(1) = 1; a(A005187(1+n)) = A087686(1+a(n)), a(A055938(n)) = A088359(a(n)), where A088359 & A087686 = numbers that occur only once & more than once in A004001.

Original entry on oeis.org

1, 3, 2, 7, 6, 5, 4, 15, 13, 14, 12, 11, 10, 9, 8, 31, 28, 29, 30, 23, 25, 27, 26, 22, 24, 21, 20, 19, 18, 17, 16, 63, 59, 60, 61, 50, 52, 62, 53, 55, 56, 58, 41, 44, 49, 57, 51, 46, 54, 48, 40, 43, 47, 45, 39, 42, 38, 37, 36, 35, 34, 33, 32, 127, 122, 123, 124, 108, 110, 125, 111, 113, 114, 126, 89, 92, 117, 115, 118, 94, 119, 121
Offset: 1

Views

Author

Antti Karttunen, Sep 03 2016

Keywords

Crossrefs

Inverse: A276343.
Similar or related permutations: A233275, A233277, A267112, A276346, A276442.

Programs

Formula

a(1)=1; for n > 1, if A079559(n)=1 [when n is in A005187], a(n) = A087686(1+a(A213714(n)-1)), otherwise a(n) = A088359(a(A234017(n))).
As a composition of other permutations:
a(n) = A267112(A233275(n)).
a(n) = A276442(A233277(n)).

A276346 Permutation of natural numbers: a(1) = 1; a(A005187(1+n)) = A088359(a(n)), a(A055938(n)) = A087686(1+a(n)), where A088359 & A087686 = numbers that occur only once & more than once in A004001.

Original entry on oeis.org

1, 2, 3, 5, 4, 7, 6, 10, 12, 9, 13, 8, 15, 14, 11, 19, 24, 22, 18, 27, 21, 23, 17, 29, 28, 25, 16, 31, 30, 26, 20, 36, 45, 43, 40, 54, 51, 35, 49, 42, 39, 41, 58, 48, 53, 34, 52, 38, 50, 44, 61, 60, 33, 59, 56, 55, 46, 32, 63, 62, 57, 47, 37, 69, 83, 81, 78, 102, 99, 74, 97, 93, 91, 68, 116, 112, 80, 88, 77, 109, 73, 75, 96, 90
Offset: 1

Views

Author

Antti Karttunen, Sep 03 2016

Keywords

Crossrefs

Inverse: A276345.
Similar or related permutations: A233275, A233277, A267112, A276344, A276442.

Programs

Formula

a(1)=1; for n > 1, if A079559(n)=1 [when n is in A005187], a(n) = A088359(a(A213714(n)-1)), otherwise a(n) = A087686(1+a(A234017(n))).
As a composition of other permutations:
a(n) = A276442(A233275(n)).
a(n) = A267112(A233277(n)).
Previous Showing 11-18 of 18 results.