OFFSET

1,5

COMMENTS

The graph makes it apparent that there are fewer primes generated when the prime p increases its length from 3 to 4 and 4 to 5 digits. - T. D. Noe, May 03 2013

LINKS

T. D. Noe, Table of n, a(n) for n = 1..10000

EXAMPLE

a(2)=1 since second prime 3 generates 23. Also a(7)=2 since for the seventh prime 17 we have two primes 317 and 1117.

MATHEMATICA

con[x_, y_] := FromDigits[Join[IntegerDigits[Prime[x]], IntegerDigits[Prime[y]]]]; t={}; Do[c=0; Do[If[PrimeQ[con[i, n]], c=c+1], {i, n}]; AppendTo[t, c], {n, 78}]; t

CROSSREFS

KEYWORD

nonn,base

AUTHOR

Jayanta Basu, May 02 2013

STATUS

approved