A141603 Odd composites of the form n-(p(n+2)-p(n))/(p(n+1)-p(n-1)), where p(n)=n-th prime.

9, 21, 25, 27, 33, 63, 77, 81, 93, 105, 125, 143, 147, 153, 165, 171, 175, 185, 235, 243, 247, 249, 255, 273, 285, 301, 321, 335, 345, 363, 405, 437, 473, 475, 483, 517, 529, 533, 559, 567, 579, 585, 591, 603, 627, 671, 689, 711, 767, 789, 793, 825, 861, 873, 891, 897

Offset

1,1

Comments

Entries are not repeated and shown in natural order.

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Example

n=10: 10-(37-29)/(31-23)=9=a(1).
n=22: 22-(89-79)/(83-73)=21=a(2).
n=26: 26-(107-101)/(103-97)=25=a(3).
n=28: 28-(113-107)/(109-103)=27=a(4).
n=34: 34-(151-139)/(149-137)=33=a(5).

Mathematica

f[{a_, b_, c_, d_}]:=(d-b)/(c-a); Select[Table[n-f[Prime[Range[n-1, n+2]]], {n, 2, 1000}], OddQ[#]&&CompositeQ[#]&]//Union (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Dec 15 2018 *)

Crossrefs

Cf. A000040.

Sequence in context: A067887 A345330 A174870 * A262748 A138786 A305733

Adjacent sequences: A141600 A141601 A141602 * A141604 A141605 A141606

Keyword

nonn

Author

Juri-Stepan Gerasimov, Sep 10 2008

Extensions

Corrected and extended by R. J. Mathar, Sep 26 2008

Status

approved