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.

A166724 a(n) = PrimePi(A166546(n)).

Original entry on oeis.org

0, 1, 2, 3, 3, 4, 4, 4, 5, 5, 6, 6, 6, 7, 7, 8, 8, 8, 8, 9, 9, 9, 9, 10, 11, 11, 11, 11, 11, 12, 12, 12, 13, 14, 14, 14, 14, 15, 15, 15, 15, 15, 16, 16, 16, 16, 17, 17, 18, 18, 18, 18, 19, 19, 19, 20, 20, 21, 21, 21, 21, 21, 22, 22, 22, 23, 23, 23, 23, 23, 24, 24, 24, 24, 24, 24, 24
Offset: 1

Views

Author

Giovanni Teofilatto, Oct 20 2009

Keywords

Crossrefs

Cf. A166546.

Programs

  • Maple
    A166546 := proc(n) option remember; local a; if n = 1 then 1; else for a from procname(n-1)+1 do if isprime(1+numtheory[tau](a)) then return a; end if; end do ; end if; end proc: A166724 := proc(n) numtheory[pi](A166546(n)) ; end proc: seq(A166724(n),n=1..80) ; # R. J. Mathar, Jan 30 2010

Extensions

Corrected (one 14 inserted) by R. J. Mathar, Jan 30 2010

A176342 Phi(A166546(n)).

Original entry on oeis.org

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

Views

Author

Giovanni Teofilatto, Apr 15 2010

Keywords

Crossrefs

Cf. A000010, A166546.

Extensions

Corrected (an early 2 removed, a 24 replaced by 36) by R. J. Mathar, Apr 22 2010

A167530 The length of the n-th run of identical consecutive values of A166724.

Original entry on oeis.org

1, 1, 1, 2, 3, 2, 3, 2, 4, 4, 1, 5, 3, 1, 4, 5, 4, 2, 4, 3, 2, 5, 3, 5, 8, 3, 1, 2, 2, 3, 12, 2, 4, 1, 9, 2, 4, 6, 3, 4, 5, 2, 5, 1, 2, 2, 12, 11, 3, 2, 1, 5, 1, 7, 4, 5, 5, 2, 5, 4, 1, 6, 12, 3, 2, 4, 9, 5, 8, 2, 3, 4, 5, 5, 3, 4, 5, 8, 2, 6, 8
Offset: 1

Views

Author

Giovanni Teofilatto, Nov 05 2009

Keywords

Crossrefs

Cf. A166724.

Programs

  • Maple
    A166546 := proc(n) option remember; local a; if n = 1 then 1; else for a from procname(n-1)+1 do if isprime(1+numtheory[tau](a)) then return a; end if; end do ; end if; end proc: A166724 := proc(n) numtheory[pi](A166546(n)) ; end proc: A166724 := proc(n) option remember ; numtheory[pi](A166546(n)) ; end proc: A167530 := proc(nmax) ol := 0 ; ct := 1 ; for n from 2 to nmax do if A166724(n) <> ol then printf("%d,",ct) ; ct := 1 ; else ct := ct+1 ; end if; ol := A166724(n) ; end do ; return ; end proc: A167530(400) ; # R. J. Mathar, Feb 01 2010

Extensions

Definition corrected by Giovanni Teofilatto, Jan 30 2010
More terms from R. J. Mathar, Feb 01 2010
Name clarified by Jason Kimberley, Aug 09 2018

A167913 Product of the n-th run of identical consecutive values of A166724.

Original entry on oeis.org

0, 1, 2, 9, 64, 25, 216, 49, 4096, 6561, 10, 161051, 1728, 13, 38416, 759375, 65536, 289, 104976, 6859, 400, 4084101, 10648, 6436343, 110075314176, 15625, 26, 729, 784, 24389, 531441000000000000, 961, 1048576, 33, 60716992766464, 1225
Offset: 1

Views

Author

Giovanni Teofilatto, Nov 15 2009

Keywords

Crossrefs

Cf. A166724.

Programs

  • Maple
    A166546 := proc(n) option remember; local a; if n = 1 then 1; else for a from procname(n-1)+1 do if isprime(1+numtheory[tau](a)) then return a; end if; end do ; end if; end proc: A166724 := proc(n) numtheory[pi](A166546(n)) ; end proc: A167913 := proc(nmax) ol := 0 ; a := 1; for n from 1 to nmax do if A166724(n) <> ol then printf("%d,",a) ; a := A166724(n) ; else a := a*A166724(n) ; end if; ol := A166724(n) ; end do ; end proc: A167913(280) : # R. J. Mathar, Jan 30 2010

Extensions

a(15) corrected and terms beyond a(25) provided by R. J. Mathar, Jan 30 2010
Name clarified by Jason Kimberley, Jul 02 2018

A176238 Natural numbers n such that d(d(n)+1) > 2.

Original entry on oeis.org

4, 9, 16, 24, 25, 30, 36, 40, 42, 49, 54, 56, 64, 66, 70, 78, 81, 88, 100, 102, 104, 105, 110, 114, 121, 128, 130, 135, 136, 138, 144, 152, 154, 165, 169, 170, 174, 182, 184, 186, 189, 190, 192, 195, 196, 222, 225, 230, 231, 232, 238, 240, 246, 248, 250, 255
Offset: 1

Views

Author

Giovanni Teofilatto, Apr 12 2010

Keywords

Comments

Complement to A166546.

Links

Crossrefs

Cf. A000005, A166546.

Programs

  • Mathematica
    Select[Range[300],DivisorSigma[0,DivisorSigma[0,#]+1]>2&] (* Harvey P. Dale, Jul 15 2021 *)

Extensions

Extended by Giovanni Teofilatto, Apr 14 2010
Corrected (192 and 240 inserted) by R. J. Mathar, Apr 22 2010
Showing 1-5 of 5 results.

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

Content is available under The OEIS End-User License Agreement.