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.

A324198 a(n) = gcd(n, A276086(n)), where A276086 is the primorial base exp-function.

Original entry on oeis.org

1, 1, 1, 3, 1, 1, 1, 1, 1, 3, 5, 1, 1, 1, 1, 15, 1, 1, 1, 1, 5, 3, 1, 1, 1, 25, 1, 3, 1, 1, 1, 1, 1, 3, 1, 7, 1, 1, 1, 3, 5, 1, 7, 1, 1, 15, 1, 1, 1, 7, 25, 3, 1, 1, 1, 5, 7, 3, 1, 1, 1, 1, 1, 21, 1, 1, 1, 1, 1, 3, 35, 1, 1, 1, 1, 75, 1, 7, 1, 1, 5, 3, 1, 1, 7, 5, 1, 3, 1, 1, 1, 7, 1, 3, 1, 1, 1, 1, 49, 3, 5, 1, 1, 1, 1, 105
Offset: 0

Views

Author

Antti Karttunen, Feb 25 2019

Keywords

Crossrefs

Cf. A324583 (positions of ones), A324584 (and terms larger than one).
Cf. A371098 (odd bisection), A371099 [= a(36n+9)].
Cf. also A328231.

Programs

  • Mathematica
    Array[Block[{i, m, n = #, p}, m = i = 1; While[n > 0, p = Prime[i]; m *= p^Mod[n, p]; n = Quotient[n, p]; i++]; GCD[#, m]] &, 106, 0] (* Michael De Vlieger, Feb 04 2022 *)
  • PARI
    A276086(n) = { my(i=0,m=1,pr=1,nextpr); while((n>0),i=i+1; nextpr = prime(i)*pr; if((n%nextpr),m*=(prime(i)^((n%nextpr)/pr));n-=(n%nextpr));pr=nextpr); m; };
    A324198(n) = gcd(n,A276086(n));
    
  • PARI
    A324198(n) = { my(m=1, p=2, orgn=n); while(n, m *= (p^min(n%p,valuation(orgn,p))); n = n\p; p = nextprime(1+p)); (m); }; \\ Antti Karttunen, Oct 21 2019

Formula

a(n) = gcd(n, A276086(n)).
From Antti Karttunen, Oct 21 2019: (Start)
A000005(a(n)) = A327168(n).
a(A328316(n)) = A328323(n).
a(n) = A324580(n) / A328584(n).
(End)

A323879 Number of divisors d of n such that A276154(d) divides n.

Original entry on oeis.org

0, 1, 0, 1, 0, 2, 0, 1, 0, 1, 0, 3, 0, 1, 0, 1, 0, 2, 0, 1, 0, 1, 0, 4, 0, 1, 0, 1, 0, 3, 0, 1, 0, 1, 0, 3, 0, 1, 0, 1, 0, 2, 0, 2, 0, 1, 0, 4, 0, 1, 0, 1, 0, 2, 0, 1, 0, 1, 0, 5, 0, 1, 0, 1, 0, 2, 0, 1, 0, 2, 0, 5, 0, 1, 0, 1, 0, 2, 0, 1, 0, 1, 0, 3, 0, 1, 0, 2, 0, 4, 0, 1, 0, 1, 0, 4, 0, 1, 0, 1, 0, 2, 0, 1, 0
Offset: 1

Views

Author

Antti Karttunen, Feb 07 2019

Keywords

Crossrefs

Cf. also A323878.

Programs

Formula

a(n) = Sum_{d|n} [A276154(d)|n], where [ ] is the Iverson bracket.

A327168 Number of common divisors of n and A276086(n), with a(0) = 1.

Original entry on oeis.org

1, 1, 1, 2, 1, 1, 1, 1, 1, 2, 2, 1, 1, 1, 1, 4, 1, 1, 1, 1, 2, 2, 1, 1, 1, 3, 1, 2, 1, 1, 1, 1, 1, 2, 1, 2, 1, 1, 1, 2, 2, 1, 2, 1, 1, 4, 1, 1, 1, 2, 3, 2, 1, 1, 1, 2, 2, 2, 1, 1, 1, 1, 1, 4, 1, 1, 1, 1, 1, 2, 4, 1, 1, 1, 1, 6, 1, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 2, 1, 1, 1, 2, 1, 2, 1, 1, 1, 1, 3, 2, 2, 1, 1, 1, 1, 8
Offset: 0

Views

Author

Antti Karttunen, Sep 19 2019

Keywords

Crossrefs

Programs

  • PARI
    A276086(n) = { my(i=0,m=1,pr=1,nextpr); while((n>0),i=i+1; nextpr = prime(i)*pr; if((n%nextpr),m*=(prime(i)^((n%nextpr)/pr));n-=(n%nextpr));pr=nextpr); m; };
    A327168(n) = numdiv(gcd(n,A276086(n)));

Formula

a(n) = A000005(A324198(n)).
a(n) = 1+A001222(A327167(n)) for n >= 1.

A323880 Number of divisors d > 1 of n such that A003415(d) divides n, where A003415 gives the arithmetic derivative of n.

Original entry on oeis.org

0, 1, 1, 2, 1, 2, 1, 2, 1, 2, 1, 3, 1, 2, 2, 2, 1, 3, 1, 3, 2, 2, 1, 4, 1, 2, 2, 3, 1, 4, 1, 3, 2, 2, 2, 4, 1, 2, 2, 3, 1, 3, 1, 3, 2, 2, 1, 5, 1, 3, 2, 3, 1, 4, 2, 3, 2, 2, 1, 5, 1, 2, 2, 3, 2, 3, 1, 3, 2, 4, 1, 5, 1, 2, 2, 3, 2, 3, 1, 3, 2, 2, 1, 4, 2, 2, 2, 3, 1, 5, 2, 3, 2, 2, 2, 6, 1, 3, 2, 4, 1, 3, 1, 3, 3
Offset: 1

Views

Author

Antti Karttunen, Feb 07 2019

Keywords

Crossrefs

Cf. A003415.
Cf. also A173441, A323878, A323879.

Programs

  • PARI
    A003415(n) = {my(fac); if(n<1, 0, fac=factor(n); sum(i=1, matsize(fac)[1], n*fac[i, 2]/fac[i, 1]))}; \\ From A003415
    A323880(n) = sumdiv(n,d,(d>1)&&!(n%A003415(d)));

Formula

a(n) = Sum_{d|n, d>1} [A003415(d)|n], where [ ] is the Iverson bracket, and A003415 gives the arithmetic derivative of n.

A324283 Multiplicative with a(p^e) = A276086(p^e).

Original entry on oeis.org

1, 3, 6, 9, 18, 18, 10, 15, 30, 54, 90, 54, 50, 30, 108, 225, 450, 90, 250, 162, 60, 270, 2250, 90, 1250, 150, 3750, 90, 11250, 324, 14, 21, 540, 1350, 180, 270, 70, 750, 300, 270, 630, 180, 350, 810, 540, 6750, 3150, 1350, 1750, 3750, 2700, 450, 15750, 11250, 1620, 150, 1500, 33750, 78750, 972, 98, 42, 300, 441, 900
Offset: 1

Views

Author

Antti Karttunen, Feb 20 2019

Keywords

Crossrefs

Programs

  • PARI
    A276086(n) = { my(i=0,m=1,pr=1,nextpr); while((n>0),i=i+1; nextpr = prime(i)*pr; if((n%nextpr),m*=(prime(i)^((n%nextpr)/pr));n-=(n%nextpr));pr=nextpr); m; };
    A324283(n) = { my(f=factor(n)); prod(i=1, #f~, A276086(f[i,1]^f[i,2])); };
Showing 1-5 of 5 results.