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

Offset: 1

Author

Juri-Stepan Gerasimov, Nov 03 2009

Keywords

• nonn

Examples

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

Crossrefs

Cf. A001097, A164276.

Programs

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

Extensions

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