A173229 - OEIS

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A173229

a(n) is the n-th number m such that 6m-1 is composite minus the n-th number k such that 6k+1 is composite.

1

2, 3, 4, 2, 5, 2, 4, 4, 3, 3, 5, 4, 2, 1, 2, 5, 6, 7, 7, 6, 6, 6, 4, 7, 5, 4, 6, 4, 4, 4, 4, 5, 5, 6, 5, 7, 8, 7, 6, 6, 6, 8, 8, 9, 9, 10, 8, 8, 12, 8, 9, 8, 9, 8, 8, 8, 7, 8, 7, 8, 6, 4, 3, 4, 4, 6, 7, 6, 6, 6, 8, 6, 6, 5, 5, 6, 8, 7, 10, 9, 9, 9, 11, 11, 11, 12, 11, 10, 9, 7, 10, 8, 8, 6, 6, 6, 4, 5, 5, 7

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OFFSET

1,1

COMMENTS

A046953 U A046954(without zero) = A067611 where A067611 U A002822 U A171696 = A001477.

LINKS

Table of n, a(n) for n=1..100.

FORMULA

a(n) = A046953(n) - A046954(n+1).

EXAMPLE

a(1) = 6 - 4 = 2;

a(2) = 11 - 8 = 3;

a(3) = 13 - 9 = 4.

MAPLE

A046953 := proc(n) if n = 1 then 6 ; else for a from procname(n-1)+1 do if not isprime(6*a-1) then return a; end if; end do: end if; end proc:

A046954 := proc(n) if n = 1 then 0 ; else for a from procname(n-1)+1 do if not isprime(6*a+1) then return a; end if; end do: end if; end proc:

A173229 := proc(n) A046953(n)-A046954(n+1) ; end proc:

seq(A173229(n), n=1..120) ; # R. J. Mathar, May 02 2010

CROSSREFS

Cf. A001477, A002822, A067611, A046953, A046954, A171696.

Sequence in context: A268444 A117826 A322604 * A366296 A191248 A323156

Adjacent sequences: A173226 A173227 A173228 * A173230 A173231 A173232

KEYWORD

nonn

AUTHOR

Juri-Stepan Gerasimov, Feb 13 2010, Feb 14 2010

EXTENSIONS

Corrected from a(63) onwards by R. J. Mathar, May 02 2010

STATUS

approved