A113590 Least multiple of prime(n) containing only prime digits (2,3,5,7).

2, 3, 5, 7, 22, 52, 255, 57, 23, 232, 372, 37, 533, 2322, 235, 53, 2537, 732, 335, 355, 73, 237, 332, 2225, 2522, 2222, 2575, 535, 327, 2373, 22225, 2227, 7535, 3753, 2235, 755, 2355, 7335, 27555, 23355, 537, 2353, 573, 772, 27777, 5373, 2532, 223, 227, 5725, 233

Offset: 1

Author

Amarnath Murthy, Nov 07 2005

Keywords

• base
• easy
• nonn

Comments

a(n) = prime(n) if prime(n) is in A019546.

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A019546, A113591.

Programs

Maple

N:= 100: # to get a(1)..a(N)
pn:= ithprime(N):
count:= 0:
digs:= [2,3,5,7]:
for d from 1 while count < N do
for m from 4^d to 2*4^d-1 while count < N do
  L:= convert(m,base,4);
  n:= add(digs[L[i]+1]*10^(i-1),i=1..nops(L)-1);
  ps:= select(p -> p <= pn and not assigned(A[p]), numtheory:-factorset(n));
  count:= count + nops(ps);
  for p in ps do A[p]:= n od:
od od:
seq(A[ithprime(i)],i=1..N); # Robert Israel, Dec 27 2018

Extensions

More terms from Nick Woods (njw130(AT)psu.edu), Apr 25 2006

a(44) and a(50) corrected by Robert Israel, Dec 27 2018