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.

A245821 Permutation of natural numbers: a(n) = A091205(A245703(n)).

Original entry on oeis.org

1, 2, 3, 4, 5, 9, 7, 6, 8, 12, 11, 15, 23, 81, 18, 10, 17, 30, 13, 162, 27, 36, 19, 24, 16, 25, 38, 46, 37, 45, 31, 135, 14, 20, 50, 57, 47, 69, 21, 55, 83, 115, 419, 87, 60, 210, 61, 42, 54, 26, 90, 28, 29, 35, 32, 63, 171, 52, 59, 138, 113, 180, 111, 48, 88, 39, 41, 621, 72, 22, 953, 230, 103, 207, 126, 64, 33, 243
Offset: 1

Views

Author

Antti Karttunen, Aug 02 2014

Keywords

Crossrefs

Inverse: A245822.
Other related permutations: A091205, A245703, A245815.
Fixed points: A245823.

Programs

  • PARI
    allocatemem(234567890);
    v014580 = vector(2^18);
    v091226 = vector(2^22);
    v091242 = vector(2^22);
    isA014580(n)=polisirreducible(Pol(binary(n))*Mod(1, 2)); \\ This function from Charles R Greathouse IV
    i=0; j=0; n=2; while((n < 2^22), if(isA014580(n), i++; v014580[i] = n; v091226[n] = v091226[n-1]+1, j++; v091242[j] = n; v091226[n] = v091226[n-1]); n++);
    A014580(n) = v014580[n];
    A091226(n) = v091226[n];
    A091242(n) = v091242[n];
    A091205(n) = if(n<=1, n, if(isA014580(n), prime(A091205(A091226(n))), {my(irfs, t); irfs=subst(lift(factor(Mod(1, 2)*Pol(binary(n)))), x, 2); irfs[,1]=apply(t->A091205(t), irfs[,1]); factorback(irfs)}));
    A245703(n) = if(1==n, 1, if(isprime(n), A014580(A245703(primepi(n))), A091242(A245703(n-primepi(n)-1))));
    A245821(n) = A091205(A245703(n));
    for(n=1, 10001, write("b245821.txt", n, " ", A245821(n)));
    
  • Scheme
    (define (A245821 n) (A091205 (A245703 n)))

Formula

a(n) = A091205(A245703(n)).
Other identities. For all n >= 1, the following holds:
A078442(a(n)) = A078442(n), A049076(a(n)) = A049076(n). [Preserves "the order of primeness of n"].
a(p_n) = p_{a(n)} where p_n is the n-th prime, A000040(n).
a(n) = A049084(a(A000040(n))). [Thus the same permutation is induced also when it is restricted to primes].
A245815(n) = A062298(a(A018252(n))). [While restriction to nonprimes induces another permutation].

A245813 Permutation of natural numbers induced when A091205 is restricted to {1} and binary codes for polynomials reducible over GF(2): a(1) = 1, a(n) = A062298(A091205(A091242(n-1))).

Original entry on oeis.org

1, 2, 5, 3, 4, 9, 11, 7, 6, 18, 10, 59, 20, 25, 16, 8, 50, 15, 32, 31, 12, 13, 38, 21, 41, 125, 85, 43, 17, 45, 52, 35, 22, 19, 103, 105, 33, 24, 14, 190, 68, 27, 66, 28, 161, 29, 80, 26, 54, 46, 177, 84, 258, 34, 180, 64, 90, 70, 507, 37, 196, 96, 39, 110, 430, 92, 78, 75, 600, 48, 40, 82, 213, 218, 71, 23, 87, 72, 51, 132, 30
Offset: 1

Views

Author

Antti Karttunen, Aug 16 2014

Keywords

Crossrefs

Inverse: A245814.
Related permutations: A091205, A245815, A245820.

Programs

  • PARI
    allocatemem(234567890);
    v091226 = vector(2^22);
    v091242 = vector(2^22);
    isA014580(n)=polisirreducible(Pol(binary(n))*Mod(1, 2)); \\ This function from Charles R Greathouse IV
    i=0; j=0; n=2; while((n < 2^22), if(isA014580(n), i++; v091226[n] = v091226[n-1]+1, j++; v091242[j] = n; v091226[n] = v091226[n-1]); n++);
    A062298(n) = n-primepi(n);
    A091226(n) = v091226[n];
    A091242(n) = v091242[n];
    A091205(n) = if(n<=1, n, if(isA014580(n), prime(A091205(A091226(n))), {my(irfs, t); irfs=subst(lift(factor(Mod(1, 2)*Pol(binary(n)))), x, 2); irfs[,1]=apply(t->A091205(t), irfs[,1]); factorback(irfs)}));
    A245813(n) = if(n<=1, n, A062298(A091205(A091242(n-1))));
    for(n=1, 10001, write("b245813.txt", n, " ", A245813(n)));
    
  • Scheme
    (define (A245813 n) (if (<= n 1) n (A062298 (A091205 (A091242 (- n 1))))))

Formula

a(1) = 1, and for n > 1, a(n) = A062298(A091205(A091242(n-1))).
As a composition of related permutations:
a(n) = A245815(A245820(n)).

A245816 Permutation of natural numbers induced when A245822 is restricted to nonprime numbers: a(n) = A062298(A245822(A018252(n))).

Original entry on oeis.org

1, 2, 4, 5, 3, 10, 6, 22, 7, 16, 9, 23, 27, 51, 15, 17, 35, 13, 37, 11, 39, 56, 69, 38, 14, 18, 48, 78, 33, 120, 20, 19, 46, 67, 24, 62, 42, 34, 28, 73, 25, 103, 31, 206, 40, 55, 68, 92, 300, 26, 76, 50, 99, 65, 157, 281, 165, 184, 8, 121, 134, 277, 423, 30, 47, 36, 223, 70, 514, 75, 101, 116, 236, 139, 74
Offset: 1

Views

Author

Antti Karttunen, Aug 02 2014

Keywords

Comments

This permutation is induced when A245822 is restricted to nonprimes, A018252, the first column of A114537, but equally, when it is restricted to column 2 (A007821), column 3 (A049078), etc. of that square array, or alternatively, to the successive rows of A236542.
The sequence of fixed points f(n) begins as 1, 2, 15, 142, 548, 1694, 54681. A018252(f(n)) gives the nonprime terms of A245823.

Crossrefs

Inverse: A245815.
Related permutations: A245814, A245820, A245822.

Programs

Formula

a(n) = A062298(A245822(A018252(n))).
As a composition of related permutations:
a(n) = A245820(A245814(n)).
Also following holds for all n >= 1:
etc.

A245819 Permutation of natural numbers induced when A245703 is restricted to nonprime numbers: a(n) = 1+A091245(A245703(A018252(n))).

Original entry on oeis.org

1, 2, 3, 4, 5, 8, 6, 12, 7, 9, 13, 26, 10, 14, 18, 11, 15, 48, 19, 20, 35, 16, 21, 32, 25, 17, 22, 63, 27, 56, 28, 138, 46, 23, 29, 43, 34, 38, 24, 30, 80, 60, 36, 88, 72, 37, 167, 42, 59, 31, 39, 55, 45, 62, 50, 33, 40, 100, 77, 320, 47, 92, 109, 90, 49, 201, 54, 98, 76, 41, 51
Offset: 1

Views

Author

Antti Karttunen, Aug 16 2014

Keywords

Crossrefs

Inverse: A245820.
Related permutations: A245703, A245814, A245815.

Programs

Formula

a(1) = 1, and for n > 1, a(n) = 1 + A245703(n-1).
a(n) = 1+A091245(A245703(A018252(n))). [Induced when A245703 is restricted to nonprime numbers].
a(n) = 1+A091226(A245703(A008578(n))). [Induced also when A245703 is restricted to noncomposite numbers].
As a composition of related permutations:
a(n) = A245814(A245815(n)).
Showing 1-4 of 4 results.