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 1-3 of 3 results.

A340145 Dirichlet inverse of A247074(x) = phi(x)/(Product_{primes p dividing x} gcd(p-1, x-1)).

Original entry on oeis.org

1, -1, -1, -1, -1, 0, -1, -1, -2, -2, -1, 1, -1, -4, 0, -1, -1, 1, -1, 1, -1, -8, -1, 2, -4, -10, -4, 9, -1, 2, -1, -1, -3, -14, -4, 3, -1, -16, -4, 4, -1, 4, -1, 1, 4, -20, -1, 3, -6, -5, -6, 17, -1, 4, -8, -10, -7, -26, -1, 6, -1, -28, 0, -1, -1, 24, -1, 1, -9, 18, -1, 4, -1, -34, 1, 25, -13, 10, -1, 7, -8, -38, -1
Offset: 1

Views

Author

Antti Karttunen, Dec 29 2020

Keywords

Crossrefs

Cf. A247074.
Cf. also A340142, A340144, A340146.

Programs

  • PARI
    up_to = 65537;
    A247074(n) = { my(f=factor(n)); eulerphi(f)/prod(i=1, #f~, gcd(f[i, 1]-1, n-1)); }; \\ From A247074
    DirInverse(v) = { my(u=vector(#v)); u[1] = (1/v[1]); for(n=2, #v, u[n] = -sumdiv(n, d, if(dA247074(n)));
    A340145(n) = v340145[n];

A340190 Möbius transform of A063994(x) = Product_{primes p dividing x} gcd(p-1, x-1).

Original entry on oeis.org

1, 0, 1, 0, 3, -1, 5, 0, 0, -3, 9, 0, 11, -5, -1, 0, 15, 0, 17, 0, -3, -9, 21, 0, 0, -11, 0, 2, 27, 1, 29, 0, -7, -15, -5, 0, 35, -17, -9, 0, 39, 3, 41, 0, 4, -21, 45, 0, 0, 0, -13, 2, 51, 0, -9, -2, -15, -27, 57, 0, 59, -29, 0, 0, 1, 11, 65, 0, -19, 7, 69, 0, 71, -35, 0, 2, -11, 9, 77, 0, 0, -39, 81, -2, -3, -41, -25
Offset: 1

Views

Author

Antti Karttunen, Dec 31 2020

Keywords

Crossrefs

Programs

  • PARI
    A063994(n) = { my(f=factor(n)); prod(i=1, #f~, gcd(f[i, 1]-1, n-1)); };
    A340190(n) = sumdiv(n,d,moebius(n/d)*A063994(d));

Formula

a(n) = Sum_{d|n} A008683(n/d) * A063994(d).
a(n) = A063994(n) - A340191(n).

A340144 Numerators of the sequence whose Dirichlet convolution with itself yields sequence A247074(x) = phi(x)/(Product_{primes p dividing x} gcd(p-1, x-1)).

Original entry on oeis.org

1, 1, 1, 7, 1, 3, 1, 25, 11, 7, 1, 19, 1, 11, 3, 363, 1, 31, 1, 43, 5, 19, 1, 63, 19, 23, 61, 3, 1, 19, 1, 1335, 9, 31, 11, 189, 1, 35, 11, 139, 1, 29, 1, 115, 7, 43, 1, 867, 27, 127, 15, 11, 1, 163, 19, 279, 17, 55, 1, 93, 1, 59, 51, 9923, 5, -15, 1, 187, 21, 3, 1, 615, 1, 71, 55, 19, 29, 59, 1, 1875, 1363, 79, 1, 203
Offset: 1

Views

Author

Antti Karttunen, Dec 29 2020

Keywords

Examples

			For n = 561 = 3*11*17, its divisors d are: 1, 3, 11, 17, 33, 51, 187, 561.
For this sequence, the corresponding terms a(d) are: 1, 1, 1, 1, 9, 15, 79, -99.
For A046644, the corresponding terms are:            1, 2, 2, 2, 4,  4,  4,   8.
Convolving these ratios as Sum_{d|561} r(d)*r(n/d) = 2*((1/1)*(-99/8) + (1/2)*(79/4) + (1/2)*(15/4) + (1/2)*(9/4)) yields 1 as expected, because 561 is Carmichael number (A002997) and A247074 obtains value 1 on all of them.
		

Crossrefs

Cf. A046644 (denominators).
Cf. A247074.
Cf. also A340141, A340145, A340146.

Programs

  • PARI
    up_to = 65537;
    A247074(n) = { my(f=factor(n)); eulerphi(f)/prod(i=1, #f~, gcd(f[i, 1]-1, n-1)); }; \\ From A247074
    DirSqrt(v) = {my(n=#v, u=vector(n)); u[1]=1; for(n=2, n, u[n]=(v[n]/v[1] - sumdiv(n, d, if(d>1&&dA247074(n)));
    A340144(n) = numerator(v340144rat[n]);
Showing 1-3 of 3 results.