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.

A066793 The start of a record-breaking run of consecutive integers with an even number of prime factors.

Original entry on oeis.org

1, 9, 14, 33, 54, 140, 213, 1934, 35811, 38405, 200938, 389409, 1792209, 5606457, 8405437, 68780189, 880346227, 85910903650, 87635944146, 284340107954, 2195312273836, 2864568747364, 3155591650029
Offset: 1

Views

Author

G. L. Honaker, Jr., Jan 18 2002

Keywords

Comments

a(21) > 10^12. [From Donovan Johnson, Oct 11 2010]
a(24) > 10^13. - Giovanni Resta, Aug 01 2013
Prime factors counted with multiplicity. - Harvey P. Dale, Sep 06 2022

Crossrefs

Programs

  • Mathematica
    Table[SequencePosition[If[EvenQ[#],1,0]&/@PrimeOmega[Range[40000]],PadRight[{},n,1],1][[All,1]],{n,14}]//Flatten//Union (* The program generates the first 10 terms of the sequence. *) (* Harvey P. Dale, Sep 06 2022 *)

Extensions

Except for first 4 or 5 terms, computed by Shyam Sunder Gupta, Jan 26 2002
a(12) and a(14) corrected and a(18)-a(20) from Donovan Johnson, Oct 11 2010
a(21)-a(23) from Giovanni Resta, Aug 01 2013

A175202 a(n) is the smallest k such that the n consecutive values L(k), L(k+1), ..., L(k+n-1) = -1, where L(m) is the Liouville function A008836(m).

Original entry on oeis.org

2, 2, 11, 17, 27, 27, 170, 279, 428, 5879, 5879, 13871, 13871, 13871, 41233, 171707, 1004646, 1004646, 1633357, 5460156, 11902755, 21627159, 21627159, 38821328, 41983357, 179376463, 179376463, 179376463, 179376463, 179376463, 179376463, 179376463
Offset: 1

Views

Author

Michel Lagneau, Mar 04 2010

Keywords

Comments

L(n) = (-1)^omega(n) where omega(n) is the number of prime factors of n with multiplicity.

Examples

			a(1) = 2 and L(2) = -1;
a(2) = 2 and L(2) = L(3)= -1;
a(3) = 11 and L(11) = L(12) = L(13) = -1;
a(4) = 17 and L(17) = L(18) = L(19) = L(20) = -1.
		

References

  • H. Gupta, On a table of values of L(n), Proceedings of the Indian Academy of Sciences. Section A, 12 (1940), 407-409.
  • H. Gupta, A table of values of Liouville's function L(n), Research Bulletin of East Panjab University, No. 3 (Feb. 1950), 45-55.

Crossrefs

Programs

  • Maple
    with(numtheory):for k from 0 to 30 do : indic:=0:for n from 1 to 1000000000 while (indic=0)do :s:=0:for i from 0 to k do :if (-1)^bigomega(n+i)= -1 then s:=s+1: else fi:od:if s=k+1 and indic=0 then print(n):indic:=1:else fi:od:od:
  • Mathematica
    Table[k=1;While[Sum[LiouvilleLambda[k+i],{i,0,n-1}]!=-n,k++];k,{n,1,30}]

Extensions

a(15) and a(21) corrected by Donovan Johnson, Apr 01 2013

A233445 Start of record runs with lambda(k) = lambda(k+1) = ..., where lambda is Liouville's function A008836.

Original entry on oeis.org

1, 2, 11, 17, 27, 140, 213, 1934, 13871, 38405, 171707, 200938, 389409, 1633357, 5460156, 8405437, 41983357, 68780189, 179376463, 130292951546, 393142151459, 2100234982892, 5942636062287
Offset: 1

Views

Author

Keywords

Examples

			Lambda(1) = 1 is the first (record) run, so a(1) = 1.
Lambda(2) = lambda(3) = -1 is the second record run, so a(2) = 2.
Lambda(11) = lambda(12) = lambda(13) = -1 is the third record run, so a(3) = 11.
		

Crossrefs

Programs

  • Mathematica
    sz[n_] := Module[{t = LiouvilleLambda[n], k = n}, While[LiouvilleLambda[k++] == t]; k - n]; r = 0; Reap[For[n = 1, n <= 10^6, n++, t = sz[n]; If[t > r, r = t; Print[t, " ", n]; Sow[n]]]][[2, 1]] (* Jean-François Alcover, Oct 17 2016, adapted from PARI *)
  • PARI
    L(n)=(-1)^bigomega(n);
    sz(n)=my(t=L(n),k=n);while(L(k++)==t,);k-n
    r=0;for(n=1,1e9,t=sz(n);if(t>r,r=t;print(t" "n)))
Showing 1-3 of 3 results.