A160954 a(n+1) is the smallest prime formed by appending a single digit to a(n); a(1)=18.

18, 181, 1811, 18119, 181193, 1811939

Offset

1,1

Comments

There is no prime a(7) since 18119390 to 18119399 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)=181193,
a(6)=1811939. [Corrected by Jon E. Schoenfield, Feb 18 2019]

Maple

A160954 :=proc(n) option remember ; local d; if n =1 then 18; else for d from 1 to 9 by 2 do if isprime(10*prochame n+d) then RETURN(10*procnam n+d 0 ; fi; end:
seq(A160954(n), n=1..10) ; R. J. Mathar, May 26 2009

Mathematica

spsd[n_]:=SelectFirst[Table[10n+d, {d, {1, 3, 7, 9}}], PrimeQ]; NestList[spsd, 18, 5] (* Harvey P. Dale, Aug 02 2024 *)

Crossrefs

Cf. A000040, A160751, A160955.

Sequence in context: A140325 A199299 A155669 * A160955 A026091 A178260

Adjacent sequences: A160951 A160952 A160953 * A160955 A160956 A160957

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