OFFSET
1,1
COMMENTS
The only even nonprime digits that are the last digit of a prime are 4, 6, and 8.
EXAMPLE
k=13 is a term because 13 is prime, prime(13)=41, and concatenation(13,41) = 1341, whose largest digit is 4, an even nonprime.
k=23 is a term because 23 is prime, prime(23)=83, and the largest digit of 2383 is 8, an even nonprime.
k=61 is a term because 61 is prime, prime(61)=283, and the largest digit of 61283 is 8.
MAPLE
A054055 := proc(n) max(op(convert(n, base, 10))) ; end proc: cat2 := proc(a, b) dgs := max(1, 1+ilog10(b)) ; a*10^dgs+b ; end proc: isA155093 := proc(n) local p, m ; if isprime(n) then p := ithprime(n) ; m := A054055(cat2(n, p)) ; return m <> 2 and type(m, 'even') ; else false; end if; end proc: for i from 1 to 2400 do if isA155093(i) then printf("%d, ", i) ; fi; od: # R. J. Mathar, Oct 22 2009
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Juri-Stepan Gerasimov, Jan 20 2009
EXTENSIONS
Edited by Jon E. Schoenfield, May 07 2019
STATUS
approved