A167428 - OEIS

A167428

Smallest non-isolated (or twin) prime > n-th non-isolated nonprime.

3, 3, 11, 11, 11, 17, 17, 17, 29, 29, 29, 29, 29, 29, 29, 29, 41, 41, 41, 41, 41, 41, 41, 41, 59, 59, 59, 59, 59, 59, 59, 59, 59, 59, 59, 59, 59, 71, 71, 71, 71, 71, 71, 71, 71, 101, 101, 101, 101, 101, 101, 101, 101, 101, 101, 101, 101, 101, 101, 101, 101, 101, 101, 101

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Table of n, a(n) for n=1..64.

EXAMPLE

a(1)=3 (>0); a(2)=3 (>1); a(3)=11 (>8); a(4)=11 (>8); a(5)=11 (>10); a(6)=17 (>14).

MAPLE

A164276 := proc(n) option remember; if n = 1 then 0; else for a from procname(n-1)+1 do if isA164276(a) then return a; end if; end do; end if: end proc:

isA164276 := proc(n) not isprime(n) and ( not isprime(n+1) or not isprime(n-1) ) ; end proc:

isA001097 := proc(n) isprime(n) and ( isprime(n+2) or isprime(n-2) ); end proc:

A167428 := proc(n) for a from A164276(n)+1 do if isA001097(a) then return a; end if; end do: end proc:

seq(A167428(n), n=1..120) ; # R. J. Mathar, May 30 2010

CROSSREFS

Cf. A001097, A164276.

Sequence in context: A122167 A095019 A321082 * A318961 A309798 A068594

Adjacent sequences: A167425 A167426 A167427 * A167429 A167430 A167431

KEYWORD

nonn

AUTHOR

Juri-Stepan Gerasimov, Nov 03 2009

EXTENSIONS

Entries checked by R. J. Mathar, May 30 2010

STATUS

approved