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.

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A110841 a(n) is the number of prime factors, with multiplicity, of abs(A014509(n)).

Original entry on oeis.org

0, 0, 0, 0, 0, 0, 0, 0, 1, 4, 2, 7, 7, 2, 2, 4, 3, 3, 7, 1, 6, 4, 5, 14, 4, 9, 5, 10, 3, 11, 2, 5, 3, 7, 11, 5, 3, 4, 15, 6, 5, 19, 10, 6, 13, 15, 5, 10, 5, 5, 6, 7, 5, 15, 7, 5, 2, 13, 4, 3, 10, 5, 9, 7, 5, 4, 9, 5, 4, 1, 7, 4, 4, 5, 3, 11, 13, 10, 5, 5, 7, 6
Offset: 0

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Author

Jonathan Vos Post, Sep 16 2005

Keywords

Examples

			a(10) = 2 because A014509(10) = 529 = 23^2.
a(8) = a(19) = 1 since A014509(8) and A014509(19) are prime.
		

Crossrefs

Programs

  • PARI
    a(n) = my(b=bernfrac(2*n), c=floor(abs(b))*sign(b)); if (c==0, 0, bigomega(c)); \\ Michel Marcus, Mar 29 2020

Formula

a(n) = A001222(abs(A014509(n))).

Extensions

More terms from Michel Marcus, Mar 29 2020
a(51)-a(65) from Jinyuan Wang, Apr 02 2020
More terms from Sean A. Irvine, Jul 29 2024

A081739 a(n) = (-1/2^n)*(A000367(2^n)+1).

Original entry on oeis.org

0, 0, 452, 481832565076, 3336994692120829058949545155598207748188, 4183667308477313795108662587270037418426429056133620947343416969739965511482242658521291610836247844507748569589344
Offset: 1

Views

Author

Benoit Cloitre, Apr 06 2003

Keywords

Crossrefs

Programs

  • Mathematica
    a[n_] := -(Numerator[BernoulliB[2^(n+1)]] + 1)/2^n; Array[a, 6] (* Amiram Eldar, May 03 2025 *)
  • PARI
    a(n) = -(numerator(bernfrac(1 << (n+1))) + 1) >> n; \\ Amiram Eldar, May 03 2025

Formula

a(n) = A076547(n)-1 (Conjecture). - R. J. Mathar, Apr 22 2007
Showing 1-2 of 2 results.