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 1-7 of 7 results.

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)

A364492 a(n) = A163511(n) / gcd(n, A163511(n)).

Original entry on oeis.org

1, 2, 2, 1, 2, 9, 1, 5, 2, 3, 9, 25, 1, 15, 5, 7, 2, 81, 3, 125, 9, 25, 25, 49, 1, 9, 15, 35, 5, 21, 7, 11, 2, 81, 81, 125, 3, 375, 125, 343, 9, 225, 25, 245, 25, 49, 49, 121, 1, 135, 9, 175, 15, 105, 35, 7, 5, 21, 21, 55, 7, 33, 11, 13, 2, 729, 81, 3125, 81, 625, 125, 2401, 3, 1125, 375, 343, 125, 147, 343, 1331
Offset: 0

Views

Author

Antti Karttunen, Jul 26 2023

Keywords

Comments

Denominator of n / A163511(n).

Crossrefs

Cf. A163511, A364255, A364491 (numerators), A364493, A364496 (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);
    A163511(n) = if(!n,1,A005940(1+A054429(n)))
    A364492(n) = { my(u=A163511(n)); (u/gcd(n, u)); };
    
  • Python
    from math import gcd
    from sympy import nextprime
    def A364492(n):
        c, p, k = 1, 1, n
        while k:
            c *= (p:=nextprime(p))**(s:=(~k&k-1).bit_length())
            k >>= s+1
        return c*p//gcd(c*p,n) # Chai Wah Wu, Jul 26 2023

Formula

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

A364494 Numbers k such that k divides A163511(k).

Original entry on oeis.org

1, 2, 3, 4, 6, 8, 9, 12, 16, 18, 24, 32, 36, 48, 64, 72, 96, 105, 128, 144, 192, 210, 256, 288, 384, 420, 429, 512, 576, 768, 840, 858, 1024, 1152, 1365, 1536, 1617, 1680, 1716, 2048, 2304, 2730, 3072, 3234, 3360, 3432, 3887, 4096, 4235, 4608, 5460, 6144, 6468, 6720, 6864, 7774, 8192, 8470, 9216, 10829, 10920, 12288
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).

Crossrefs

Positions of 1's in A364491.
Cf. A163511.
Subsequences: A007283, A029744, A364495 (odd terms).
Cf. also A364295, A364496, A364497.

Programs

A364501 a(n) = n / gcd(n, A005940(n)).

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 7, 1, 9, 1, 11, 1, 13, 7, 5, 1, 17, 9, 19, 1, 3, 11, 23, 1, 25, 13, 9, 7, 29, 5, 31, 1, 33, 17, 35, 9, 37, 19, 13, 1, 41, 3, 43, 11, 9, 23, 47, 1, 49, 25, 17, 13, 53, 9, 11, 7, 57, 29, 59, 5, 61, 31, 7, 1, 65, 33, 67, 17, 69, 35, 71, 9, 73, 37, 5, 19, 7, 13, 79, 1, 81, 41, 83, 3, 17, 43, 29, 11, 89
Offset: 1

Views

Author

Antti Karttunen, Jul 28 2023

Keywords

Comments

Numerator of n / A005940(n).

Crossrefs

Cf. A005940, A364500, A364502 (denominators), A364544 (positions of 1's).
Cf. also A364491.

Programs

  • Mathematica
    nn = 89; 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[#/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 };
    A364501(n) = (n / gcd(n, A005940(n)));
    
  • PARI
    A364501(n) = { my(orgn=n,p=2,rl=0,z=1); n--; while(n, if(!(n%2), p=nextprime(1+p), rl++; if(1==(n%4), z *= p^min(rl,valuation(orgn,p)); rl=0)); n>>=1); (orgn/z); };

A366374 a(n) = n / gcd(n, A332214(n)), where A332214 is the Mersenne-prime fixing variant of permutation A163511.

Original entry on oeis.org

0, 1, 1, 1, 1, 5, 1, 1, 1, 1, 5, 11, 1, 13, 1, 3, 1, 17, 1, 19, 5, 1, 11, 23, 1, 25, 13, 27, 1, 29, 3, 1, 1, 11, 17, 5, 1, 37, 19, 39, 5, 41, 1, 43, 11, 3, 23, 47, 1, 7, 25, 51, 13, 53, 27, 11, 1, 19, 29, 59, 3, 61, 1, 63, 1, 65, 11, 67, 17, 23, 5, 71, 1, 73, 37, 3, 19, 77, 39, 79, 5, 3, 41, 83, 1, 17, 43, 87, 11, 89
Offset: 0

Views

Author

Antti Karttunen, Oct 08 2023

Keywords

Comments

Numerator of n / A332214(n).

Crossrefs

Cf. A332214, A366372, A366373, A366375 (denominators), A366376.
Cf. also A364491, A366284.

Programs

Formula

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

A366284 a(n) = n / gcd(n, A366275(n)), where A366275 is the Cat's tongue permutation.

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, 1, 13, 27, 7, 29, 15, 31, 1, 11, 17, 7, 1, 37, 19, 13, 5, 41, 7, 43, 11, 15, 23, 47, 1, 49, 1, 51, 13, 53, 27, 1, 7, 57, 29, 59, 15, 61, 31, 63, 1, 65, 11, 67, 17, 23, 7, 71, 1, 73, 37, 5, 19, 11, 13, 79, 5, 27, 41, 83, 7, 17, 43, 29, 11
Offset: 0

Views

Author

Antti Karttunen, Oct 07 2023

Keywords

Comments

Numerator of n / A366275(n).

Crossrefs

Cf. also A364491.

Programs

Formula

a(n) = n / A366283(n) = n / gcd(n, A366275(n))
Showing 1-7 of 7 results.