OFFSET
1,2
COMMENTS
Up to a(10^6), a(n) =~ 100000 + 24n + 10^(-6*n), which is almost a straight line. - Robert G. Wilson v
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
EXAMPLE
a(5) = 21 because the first prime after a(4) = 419 beginning with 5 is 521.
MAPLE
A[1]:= 1:
for n from 2 to 100 do
for m from A[n-1]+1 do
if isprime(ncat(n, m)) then A[n]:= m; break fi
od od:
seq(A[i], i=1..100); # Robert Israel, Feb 14 2021
MATHEMATICA
a[1] = 1; a[1] = 1; a[n_] := a[n] = Block[{k = IntegerDigits[n], l = a[n - 1] + 2}, While[ !PrimeQ[ FromDigits[ Join[k, IntegerDigits[l]]]], l += 2]; l]; Table[ a[n], {n, 1, 55}]
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Amarnath Murthy, Nov 20 2003
EXTENSIONS
Corrected and extended by Robert G. Wilson v, Dec 05 2003
STATUS
approved