OFFSET
1,1
LINKS
K. D. Bajpai, Table of n, a(n) for n = 1..9135
EXAMPLE
43 is in the sequence because it is prime formed from the concatenation of 4 and 3, where 3 is largest prime < 4.
1613 is in the sequence because it is prime formed from the concatenation of 16 and 13, where 13 is largest prime < 16.
MAPLE
with(numtheory): select( isprime, [seq((n*10^floor(evalf(log10(prevprime(n))+1, 100))+prevprime(n)), n=3..500)]);
P:=proc(i) local a, n, c; c:=1; for n from 3 by 1 to i do a:=n*10^floor(evalf(log10(prevprime(n))+1, 100))+prevprime(n); if (isprime(a)) then lprint(c, a); c:=c+1; fi; od; end: P(10000);
MATHEMATICA
Select[Table[FromDigits[Join[IntegerDigits[n], IntegerDigits[NextPrime[n, -1]]]], {n, 200}], PrimeQ] (* Harvey P. Dale, Oct 22 2022 *)
CROSSREFS
KEYWORD
nonn,base
AUTHOR
K. D. Bajpai, Jan 01 2017
STATUS
approved