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A176589
Numbers n such that both concatenation of divisors of n and reverse concatenation of divisors of n are noncomposites.
1
1, 3, 7, 13, 31, 97, 103, 109, 151, 181, 193, 367, 409, 439, 487, 523, 571, 601, 613, 733, 811, 823, 1069, 1117, 1279, 1483, 1489, 1579, 1597, 1789, 1831, 1867, 1897, 1939, 2161, 2203, 2239, 2251, 2269, 2281, 2437, 2503, 2509, 2539, 2659, 2671, 2689, 2953
OFFSET
1,2
COMMENTS
See A037278(n) = concatenation of divisors of n and A176558(n) = reverse concatenation of divisors of n. See A176553, A089374. Sequence of corresponding values of concatenations of divisors of a(n): {1, 13, 17, 113, 131, 197, ...), sequence of corresponding values of reverse concatenations of divisors of a(n): {1, 31, 71, 131, 311, 971, ...).
EXAMPLE
a(5) = 31; divisors of 31: 1, 31; both concatenation of divisors 131 and reverse concatenation of divisors 311 are noncomposite.
CROSSREFS
Sequence in context: A247895 A336688 A155128 * A077314 A069246 A340870
KEYWORD
nonn,base
AUTHOR
Jaroslav Krizek, Apr 21 2010
EXTENSIONS
Expanded and revised by Charles R Greathouse IV, Apr 24 2010
STATUS
approved