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A217700
Numbers n where n is a prime to the (nonzero) power of a prime, and each digit of n is also a prime to the (nonzero) power of a prime.
0
4, 8, 9, 49, 4489, 444444888889, 949488489889, 4444444488888889, 444444444888888889
OFFSET
1,1
COMMENTS
No more with 10 or fewer digits. Subsequence of A053810, prime powers of prime numbers, and of A083807, perfect powers using only digits 4,6,8,9 and 0.
EXAMPLE
a(1) = 4 = 2^2; a(2) = 8 = 2^3; a(3) = 9 = 3^2; a(4) = 49 = 7^2; a(5) = 4489 = 67^2.
PROG
(PARI) list(lim)=my(v=List(), u=[4, 8, 9]); forprime(p=2, log(lim+=.5)\log(2), forprime(q=2, lim^(1/p), if(vecsort(concat(digits(q^p), u), , 8)==u, listput(v, q^p)))); vecsort(Vec(v)) \\ Charles R Greathouse IV, Mar 19 2013
CROSSREFS
Sequence in context: A239520 A083807 A098128 * A118895 A327654 A110811
KEYWORD
nonn,base,more
AUTHOR
EXTENSIONS
a(6)-a(9) from Charles R Greathouse IV, Mar 20 2013
STATUS
approved