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 1-8 of 8 results.

A365393 Lexicographically earliest infinite sequence such that a(i) = a(j) => A364492(i) = A364492(j) for all i, j >= 0, where A364492(n) is the denominator of n / A163511(n).

Original entry on oeis.org

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

Views

Author

Antti Karttunen, Sep 06 2023

Keywords

Comments

Restricted growth sequence transform of A364492.
Question: Which sets of numbers cause the finite branches that grow off-angle from the rays emanating from the origin in the scatter plot, and why the sudden bends in some of them? Compare also to the scatter plot of A365431.

Crossrefs

Programs

  • PARI
    up_to = 65537;
    rgs_transform(invec) = { my(om = Map(), outvec = vector(length(invec)), u=1); for(i=1, length(invec), if(mapisdefined(om,invec[i]), my(pp = mapget(om, invec[i])); outvec[i] = outvec[pp] , mapput(om,invec[i],i); outvec[i] = u; u++ )); outvec; };
    A163511(n) = if(!n, 1, my(p=2, t=1); while(n>1, if(!(n%2), (t*=p), p=nextprime(1+p)); n >>= 1); (t*p));
    A364492(n) = { my(u=A163511(n)); (u/gcd(n, u)); };
    v365393 = rgs_transform(vector(1+up_to,n,A364492(n-1)));
    A365393(n) = v365393[1+n];

Formula

For all n >= 1, a(n) = a(2*n) = a(A000265(n)).

A364493 a(n) = A364491(n) * A364492(n).

Original entry on oeis.org

0, 2, 2, 1, 2, 45, 1, 35, 2, 3, 45, 275, 1, 195, 35, 105, 2, 1377, 3, 2375, 45, 175, 275, 1127, 1, 45, 195, 945, 35, 609, 105, 341, 2, 891, 1377, 875, 3, 13875, 2375, 13377, 45, 9225, 175, 10535, 275, 735, 1127, 5687, 1, 6615, 45, 8925, 195, 5565, 945, 35, 35, 399, 609, 3245, 105, 2013, 341, 819, 2, 47385, 891
Offset: 0

Views

Author

Antti Karttunen, Jul 26 2023

Keywords

Crossrefs

Programs

  • PARI
    A005940(n) = { my(p=2, t=1); n--; until(!n\=2, if((n%2), (t*=p), p=nextprime(p+1))); t };
    A054429(n) = ((3<<#binary(n\2))-n-1);
    A163511(n) = if(!n,1,A005940(1+A054429(n)))
    A364493(n) = { my(u=A163511(n)); (n/gcd(n,u))*(u/gcd(n,u)); };
    
  • Python
    from math import gcd
    from sympy import nextprime
    def A364493(n):
        c, p, k = 1, 1, n
        while k:
            c *= (p:=nextprime(p))**(s:=(~k&k-1).bit_length())
            k >>= s+1
        return n*c*p//gcd(c*p,n)**2 # Chai Wah Wu, Jul 26 2023

Formula

a(n) = lcm(n, A163511(n)) / A364255(n).
a(n) = 1 <=> A364258(n) = 0 <=> A364288(n) = 0.

A364255 a(n) = gcd(n, A163511(n)).

Original entry on oeis.org

1, 1, 2, 3, 4, 1, 6, 1, 8, 9, 2, 1, 12, 1, 2, 1, 16, 1, 18, 1, 4, 3, 2, 1, 24, 5, 2, 1, 4, 1, 2, 1, 32, 3, 2, 5, 36, 1, 2, 1, 8, 1, 6, 1, 4, 3, 2, 1, 48, 1, 10, 1, 4, 1, 2, 11, 8, 3, 2, 1, 4, 1, 2, 1, 64, 1, 6, 1, 4, 3, 10, 1, 72, 1, 2, 5, 4, 7, 2, 1, 16, 27, 2, 1, 12, 5, 2, 1, 8, 1, 6, 1, 4, 3, 2, 1, 96, 1, 2, 1, 20, 1, 2, 1, 8, 105
Offset: 0

Views

Author

Antti Karttunen, Jul 16 2023

Keywords

Crossrefs

Cf. A163511, A364257 (Dirichlet inverse), A364258, A364491, A364492, A364493.

Programs

  • PARI
    A163511(n) = if(!n,1,my(p=2, t=1); while(n>1, if(!(n%2), (t*=p), p=nextprime(1+p)); n >>= 1); (t*p));
    A364255(n) = gcd(n, A163511(n)); \\ Antti Karttunen, Sep 01 2023
  • Python
    from math import gcd
    from sympy import nextprime
    def A364255(n):
        c, p, k = 1, 1, n
        while k:
            c *= (p:=nextprime(p))**(s:=(~k&k-1).bit_length())
            k >>= s+1
        return gcd(c*p,n) # Chai Wah Wu, Jul 25 2023
    

Formula

From Antti Karttunen, Sep 01 2023: (Start)
a(n) = gcd(n, A364258(n)) = gcd(A163511(n), A364258(n)).
a(n) = n / A364491(n) = A163511(n)/ A364492(n).
(End)

A364496 Numbers k such that k is a multiple of A163511(k).

Original entry on oeis.org

0, 3, 6, 12, 24, 48, 96, 192, 384, 768, 1536, 3072, 6144, 12288, 16383, 24576, 32766, 49152, 65532, 98304, 131064, 196608, 262128, 393216, 524256, 786432, 1048512, 1572864, 2097024, 3145728, 4194048, 6291456, 8388096, 12582912, 16776192, 25165824, 33552384, 50331648, 67104768, 100663296, 134209536, 201326592
Offset: 1

Views

Author

Antti Karttunen, Jul 27 2023

Keywords

Comments

If n is present, then 2*n is also present, and vice versa.
A007283 is included as a subsequence, because it gives the known fixed points of map n -> A163511(n).
Sequence A243071(A364497(.)) sorted into ascending order.

Examples

			16383 is present, because A163511(16383) = 43, as 16383 = 2^14 - 1 and A000040(14) = 43, and 43 is a factor of 16383 = 3*43*127.
536870895 is present, because A163511(536870895) = 1177 (11*107), which divides 536870895 (3*5*11*47*107*647). See also example in A364498.
		

Crossrefs

Positions of 1's in A364492.
Subsequence of A364292.
Cf. A007283 (subsequence), A163511, A364963 (odd terms).

Programs

A364491 a(n) = n / gcd(n, A163511(n)).

Original entry on oeis.org

0, 1, 1, 1, 1, 5, 1, 7, 1, 1, 5, 11, 1, 13, 7, 15, 1, 17, 1, 19, 5, 7, 11, 23, 1, 5, 13, 27, 7, 29, 15, 31, 1, 11, 17, 7, 1, 37, 19, 39, 5, 41, 7, 43, 11, 15, 23, 47, 1, 49, 5, 51, 13, 53, 27, 5, 7, 19, 29, 59, 15, 61, 31, 63, 1, 65, 11, 67, 17, 23, 7, 71, 1, 73, 37, 15, 19, 11, 39, 79, 5, 3, 41, 83, 7, 17, 43, 87
Offset: 0

Views

Author

Antti Karttunen, Jul 26 2023

Keywords

Comments

Numerator of n / A163511(n).

Crossrefs

Cf. A163511, A364255, A364492 (denominators), A364493, A364494 (positions of 1's).

Programs

  • PARI
    A005940(n) = { my(p=2, t=1); n--; until(!n\=2, if((n%2), (t*=p), p=nextprime(p+1))); t };
    A054429(n) = ((3<<#binary(n\2))-n-1); \\ From A054429
    A163511(n) = if(!n,1,A005940(1+A054429(n)))
    A364491(n) = (n/gcd(n, A163511(n)));
    
  • Python
    from math import gcd
    from sympy import nextprime
    def A364491(n):
        c, p, k = 1, 1, n
        while k:
            c *= (p:=nextprime(p))**(s:=(~k&k-1).bit_length())
            k >>= s+1
        return n//gcd(c*p,n) # Chai Wah Wu, Jul 26 2023

Formula

a(n) = n / A364255(n) = n / gcd(n, A163511(n)).

A364502 a(n) = A005940(n) / gcd(n, A005940(n)).

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 9, 1, 7, 1, 15, 1, 25, 9, 9, 1, 11, 7, 21, 1, 5, 15, 45, 1, 49, 25, 25, 9, 125, 9, 81, 1, 13, 11, 33, 7, 55, 21, 21, 1, 77, 5, 105, 15, 35, 45, 135, 1, 121, 49, 49, 25, 245, 25, 45, 9, 343, 125, 375, 9, 625, 81, 27, 1, 17, 13, 39, 11, 65, 33, 99, 7, 91, 55, 11, 21, 25, 21, 189, 1, 143, 77, 231, 5
Offset: 1

Views

Author

Antti Karttunen, Jul 28 2023

Keywords

Comments

Denominator of n / A005940(n).

Crossrefs

Cf. A005940, A364500, A364501 (numerators), A364546 (positions of 1's).
Cf. also A364492.

Programs

  • Mathematica
    nn = 84; Array[Set[a[#], #] &, 2]; Do[If[EvenQ[n], Set[a[n], 2 a[n/2]], Set[a[n], Times @@ Power @@@ Map[{Prime[PrimePi[#1] + 1], #2} & @@ # &, FactorInteger[a[(n + 1)/2]]]]], {n, 3, nn}]; Array[a[#]/GCD[a[#], #] &, nn] (* Michael De Vlieger, Jul 28 2023 *)
  • PARI
    A005940(n) = { my(p=2, t=1); n--; until(!n\=2, if((n%2), (t*=p), p=nextprime(p+1))); t };
    A364502(n) = { my(u=A005940(n)); (u / gcd(n, u)); };

A366375 a(n) = A332214(n) / gcd(n, A332214(n)), where A332214 is the Mersenne-prime fixing variant of permutation A163511.

Original entry on oeis.org

1, 2, 2, 1, 2, 9, 1, 1, 2, 3, 9, 49, 1, 21, 1, 1, 2, 81, 3, 343, 9, 7, 49, 25, 1, 63, 21, 35, 1, 15, 1, 1, 2, 81, 81, 343, 3, 1029, 343, 125, 9, 441, 7, 175, 49, 5, 25, 961, 1, 27, 63, 245, 21, 105, 35, 31, 1, 15, 15, 217, 1, 93, 1, 11, 2, 729, 81, 16807, 81, 2401, 343, 625, 3, 3087, 1029, 35, 343, 375, 125, 29791, 9, 49
Offset: 0

Views

Author

Antti Karttunen, Oct 08 2023

Keywords

Comments

Denominator of n / A332214(n).

Crossrefs

Cf. A332214, A366372, A366373, A366374 (numerators), A366376 (rgs-transform).
Cf. also A364492, A366285.

Programs

Formula

a(n) = A332214(n) / A366373(n) = A332214(n) / gcd(n, A332214(n)).

A366285 a(n) = A366275(n) / gcd(n, A366275(n)), where A366275 is the Cat's tongue permutation.

Original entry on oeis.org

1, 2, 2, 1, 2, 9, 1, 5, 2, 3, 9, 15, 1, 25, 5, 7, 2, 81, 3, 45, 9, 25, 15, 21, 1, 5, 25, 35, 5, 49, 7, 11, 2, 81, 81, 27, 3, 225, 45, 21, 9, 375, 25, 105, 15, 49, 21, 33, 1, 625, 5, 175, 25, 245, 35, 1, 5, 343, 49, 77, 7, 121, 11, 13, 2, 729, 81, 405, 81, 225, 27, 189, 3, 1125, 225, 21, 45, 63, 21, 99, 9, 625, 375, 525
Offset: 0

Views

Author

Antti Karttunen, Oct 07 2023

Keywords

Comments

Denominator of n / A366275(n).

Crossrefs

Cf. A057889, A163511, A366275, A366282, A366283, A366284 (numerators), A366286 (rgs-transform).
Cf. also A364492.

Programs

Formula

a(n) = A366275(n) / A366283(n) = A366275(n) / gcd(n, A366275(n))
Showing 1-8 of 8 results.