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 1-5 of 5 results.

A300718 Möbius transform of A010848, number of numbers k <= n such that at least one prime factor of n is not a prime factor of k.

Original entry on oeis.org

0, 1, 2, 1, 4, 2, 6, 2, 4, 4, 10, 4, 12, 6, 8, 4, 16, 6, 18, 8, 12, 10, 22, 8, 16, 12, 12, 12, 28, 8, 30, 8, 20, 16, 24, 10, 36, 18, 24, 16, 40, 12, 42, 20, 24, 22, 46, 16, 36, 20, 32, 24, 52, 18, 40, 24, 36, 28, 58, 16, 60, 30, 36, 16, 48, 20, 66, 32, 44, 24, 70, 20, 72, 36, 40, 36, 60, 24, 78, 32, 36, 40, 82, 24, 64, 42, 56, 40, 88, 24, 72
Offset: 1

Views

Author

Antti Karttunen, Mar 11 2018

Keywords

Crossrefs

Programs

Formula

a(n) = Sum_{d|n} A008683(n/d)*A010848(d).
a(n) = A000010(n) - A300717(n).
a(n) = A010848(n) - A300720(n).

A300720 Difference between A010848 and its Möbius transform.

Original entry on oeis.org

0, 0, 0, 1, 0, 3, 0, 2, 2, 5, 0, 6, 0, 7, 6, 4, 0, 9, 0, 10, 8, 11, 0, 12, 4, 13, 6, 14, 0, 21, 0, 8, 12, 17, 10, 20, 0, 19, 14, 20, 0, 29, 0, 22, 18, 23, 0, 24, 6, 25, 18, 26, 0, 27, 14, 28, 20, 29, 0, 42, 0, 31, 24, 16, 16, 45, 0, 34, 24, 45, 0, 40, 0, 37, 30, 38, 16, 53, 0, 40, 18, 41, 0, 58, 20, 43, 30, 44, 0, 63, 18
Offset: 1

Views

Author

Antti Karttunen, Mar 12 2018

Keywords

Crossrefs

Programs

  • PARI
    A003557(n) = { my(f=factor(n)); for (i=1, #f~, f[i, 2] = max(0,f[i, 2]-1)); factorback(f); }; \\ From A003557
    A010848(n) = (n - A003557(n));
    A300720(n) = -sumdiv(n,d,(dA010848(d));

Formula

a(n) = -Sum_{d|n, dA008683(n/d)*A010848(d).
a(n) = A010848(n) - A300718(n).

A326188 a(n) = A001065(n) - A003557(n), where A001065(n) = the sum of proper divisors of n, and A003557(n) = n divided by its largest squarefree divisor.

Original entry on oeis.org

-1, 0, 0, 1, 0, 5, 0, 3, 1, 7, 0, 14, 0, 9, 8, 7, 0, 18, 0, 20, 10, 13, 0, 32, 1, 15, 4, 26, 0, 41, 0, 15, 14, 19, 12, 49, 0, 21, 16, 46, 0, 53, 0, 38, 30, 25, 0, 68, 1, 38, 20, 44, 0, 57, 16, 60, 22, 31, 0, 106, 0, 33, 38, 31, 18, 77, 0, 56, 26, 73, 0, 111, 0, 39, 44, 62, 18, 89, 0, 98, 13, 43, 0, 138, 22, 45, 32, 88, 0, 141, 20
Offset: 1

Views

Author

Antti Karttunen, Jul 11 2019

Keywords

Crossrefs

Programs

  • PARI
    A003557(n) = { my(f=factor(n)); for (i=1, #f~, f[i, 2] = f[i, 2]-1); factorback(f); }; \\ From A003557
    A326188(n) = ((sigma(n)-A003557(n))-n);

Formula

a(n) = A326187(n) - n = A000203(n) - A003557(n) - n.
a(n) = A001065(n) - A003557(n).

A326186 a(n) = n - A057521(n), where A057521 gives the powerful part of n.

Original entry on oeis.org

0, 1, 2, 0, 4, 5, 6, 0, 0, 9, 10, 8, 12, 13, 14, 0, 16, 9, 18, 16, 20, 21, 22, 16, 0, 25, 0, 24, 28, 29, 30, 0, 32, 33, 34, 0, 36, 37, 38, 32, 40, 41, 42, 40, 36, 45, 46, 32, 0, 25, 50, 48, 52, 27, 54, 48, 56, 57, 58, 56, 60, 61, 54, 0, 64, 65, 66, 64, 68, 69, 70, 0, 72, 73, 50, 72, 76, 77, 78, 64, 0, 81, 82, 80, 84
Offset: 1

Views

Author

Antti Karttunen, Jul 11 2019

Keywords

Crossrefs

Cf. also A010848.

Programs

  • PARI
    A057521(n) = { my(f=factor(n)); prod(i=1, #f~, if(f[i, 2]>1, f[i, 1]^f[i, 2], 1)); }; \\ From A057521.
    A326186(n) = (n-A057521(n));
    
  • Python
    from math import prod
    from sympy import factorint
    def A326186(n): return n-n//prod(p for p, e in factorint(n).items() if e == 1) # Chai Wah Wu, Nov 14 2022

Formula

a(n) = n - A057521(n).

A340806 a(n) = Sum_{k=1..n-1} (k^n mod n).

Original entry on oeis.org

0, 1, 3, 2, 10, 13, 21, 4, 27, 45, 55, 38, 78, 77, 105, 8, 136, 93, 171, 146, 210, 209, 253, 172, 250, 325, 243, 294, 406, 365, 465, 16, 528, 561, 595, 402, 666, 665, 741, 372, 820, 673, 903, 726, 945, 897, 1081, 536, 1029, 1125, 1275, 1170, 1378, 765, 1485
Offset: 1

Views

Author

Sebastian Karlsson, Jan 22 2021

Keywords

Crossrefs

Programs

  • Maple
    a:= n-> add(k&^n mod n, k=1..n-1):
    seq(a(n), n=1..55);  # Alois P. Heinz, Feb 13 2021
  • PARI
    a(n) = sum(k=1, n-1, lift(Mod(k, n)^n)); \\ Michel Marcus, Jan 22 2021
  • Python
    def a(n):
        return sum([pow(k,n,n) for k in range(1, n)])
    for n in range(1, 56):
        print(a(n), end=', ')
    

Formula

a(n) = n*A010848(n)/2, if n is odd.
a(n) = n*(n-1)/2, if n is both odd and squarefree.
a(p^e) = (1/2)*(p-1)*p^(2*e-1), if p is an odd prime.
a(2^e) = 2^(e-1).
Showing 1-5 of 5 results.