A160955 a(n+1) is the largest prime formed by appending a single digit to a(n); a(1)=18.

18, 181, 1811, 18119, 181199, 1811993

Offset

1,1

Comments

There is no prime a(7) since 18119930 to 18119939 are all composite.

Links

Table of n, a(n) for n=1..6.

Example

a(1)=18,
a(2)=181,
a(3)=1811,
a(4)=18119,
a(5)=181199,
a(6)=1811993. [Corrected by Jon E. Schoenfield, Feb 18 2019]

Maple

A160955 :=proc(n)
    option remember ;
    local d;
    if n =1 then
        18;
    else
        for d from 9 to 1 by -2 do
            p := 10*procname(n-1)+d ;
            if isprime(p) then
                return p;
            end if:
        end do:
    end if;
end proc:
seq(A160955(n), n=1..6) ; # R. J. Mathar, Mar 04 2026

Crossrefs

Cf. A000040, A160751, A160954.

Sequence in context: A199299 A155669 A160954 * A393588 A026091 A178260

Adjacent sequences: A160952 A160953 A160954 * A160956 A160957 A160958

Keyword

nonn,base,easy,fini,full

Author

Juri-Stepan Gerasimov, May 31 2009

Extensions

Redundant part of the definition removed by R. J. Mathar, May 21 2010

Status

approved