OFFSET
1,1
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
EXAMPLE
72 is the concatenation of primes 7 and 2. 132 is the concatenation of primes 13 and 2. 225 is the concatenation of 2, 2 and 5.
MAPLE
ccat:= proc(m, n) 10^(1+ilog10(n))*m+n end proc:
C[1]:= {2, 3, 5, 7}: P[1]:=C[1]:
for n from 2 to 3 do
P[n]:= select(isprime, {seq(i, i=10^(n-1)+1..10^n-1, 2)});
C[n]:= P[n];
for m from 1 to n-1 do
C[n]:= C[n] union {seq(seq(ccat(p, q), p =P[m]), q=C[n-m])};
od
od:
seq(op(sort(convert(remove(isprime, C[n]), list))), n=1..3); # Robert Israel, Jan 22 2020
PROG
(PARI) for(n=1, 999, !isprime(n) && is_A152242(n) && print1(n", ")) \\ M. F. Hasler, Oct 16 2009
CROSSREFS
KEYWORD
base,easy,nonn
AUTHOR
Joseph L. Pe, Jan 15 2002
EXTENSIONS
More terms from Larry Reeves (larryr(AT)acm.org), Apr 03 2002
Missing terms added by M. F. Hasler, Oct 16 2009
STATUS
approved