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 1-2 of 2 results.

A324650 a(n) = A000010(A276086(n)).

Original entry on oeis.org

1, 1, 2, 2, 6, 6, 4, 4, 8, 8, 24, 24, 20, 20, 40, 40, 120, 120, 100, 100, 200, 200, 600, 600, 500, 500, 1000, 1000, 3000, 3000, 6, 6, 12, 12, 36, 36, 24, 24, 48, 48, 144, 144, 120, 120, 240, 240, 720, 720, 600, 600, 1200, 1200, 3600, 3600, 3000, 3000, 6000, 6000, 18000, 18000, 42, 42, 84, 84, 252, 252, 168, 168, 336, 336, 1008, 1008
Offset: 0

Views

Author

Antti Karttunen, Mar 10 2019

Keywords

Comments

Terms are duplicated because phi(2*(2n+1)) = phi(2n+1) for all n >= 0.

Links

Crossrefs

Cf. A000010, A002110, A276086, A324651 (bisection).
Cf. also A267263, A276150, A324653, A324655 for omega, bigomega, sigma and tau analogs.
Cf. also A290077.

Programs

  • PARI
    A324650(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)-1)*(prime(i)^(((n%nextpr)/pr)-1)); n-=(n%nextpr));pr=nextpr); (m); };
  • 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; };
A324650(n) = eulerphi(A276086(n));

Formula

a(n) = A000010(A276086(n)).
a(2n+1) = a(2n) for all n >= 0.
For n >= 1, a(A002110(n-1)) = A000040(n)-1.

A339821 a(n) = phi(A019565(2n)), where phi is Euler totient function.

Original entry on oeis.org

1, 2, 4, 8, 6, 12, 24, 48, 10, 20, 40, 80, 60, 120, 240, 480, 12, 24, 48, 96, 72, 144, 288, 576, 120, 240, 480, 960, 720, 1440, 2880, 5760, 16, 32, 64, 128, 96, 192, 384, 768, 160, 320, 640, 1280, 960, 1920, 3840, 7680, 192, 384, 768, 1536, 1152, 2304, 4608, 9216, 1920, 3840, 7680, 15360, 11520, 23040, 46080, 92160
Offset: 0

Views

Author

Antti Karttunen, Dec 18 2020

Keywords

Crossrefs

Bisection of A339820.
Cf. A000010, A003961, A003972, A006093, A019565, A339822 (2-adic valuation).
Cf. also A324651.

Programs

  • PARI
    A019565(n) = { my(m=1, p=1); while(n>0, p = nextprime(1+p); if(n%2, m *= p); n >>= 1); (m); };
A339821(n) = eulerphi(A019565(n+n));
  • PARI
    A339821(n) = { my(m=1, p=2); while(n>0, p = nextprime(1+p); if(n%2, m *= (p-1)); n >>= 1); (m); };

Formula

If 4n = 2^e1 + 2^e2 + ... + 2^ek [e1 ... ek distinct], then a(n) = A006093(e1) * A006093(e2) * ... * A006093(ek).
a(n) = A339820(2n) = A000010(A019565(2n)) = A000010(A019565(2n+1)).
a(n) = A003972(A019565(n)) = A000010(A003961(A019565(n))).
Showing 1-2 of 2 results.

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