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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 (list; graph; refs; listen; history; text; internal format)
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, ...).

LINKS

Table of n, a(n) for n=1..48.

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: A126879 A247895 A155128 * A077314 A069246 A253850

Adjacent sequences:  A176586 A176587 A176588 * A176590 A176591 A176592

KEYWORD

nonn,base

AUTHOR

Jaroslav Krizek, Apr 21 2010

EXTENSIONS

Expanded and revised by Charles R Greathouse IV, Apr 24 2010

STATUS

approved

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Last modified February 17 12:29 EST 2020. Contains 331996 sequences. (Running on oeis4.)