A176590 Numbers n such that both concatenation of divisors of n and reverse concatenation of divisors of n are nonprime.

1, 2, 5, 6, 8, 10, 11, 12, 14, 15, 16, 17, 18, 20, 22, 23, 24, 26, 27, 28, 29, 30, 32, 33, 34, 35, 36, 38, 40, 41, 42, 44, 45, 46, 47, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 68, 69, 70, 71, 72, 74, 75, 76, 77, 78, 80, 81, 82, 83, 84, 85, 86, 87, 88

Offset

1,2

Comments

See A037278(n) = concatenation of divisors of n and A176558(n) = reverse concatenation of divisors of n. See A176554, A175354. Sequence of corresponding values of concatenations of divisors of a(n): {1, 12, 15, 1236, 1248, 12510, 111, ...), sequence of corresponding values of reverse concatenations of divisors of a(n): {1, 21, 51, 6321, 8421, 10521, 111, ...).

Links

Table of n, a(n) for n=1..72.

Example

For n = 6; a(6) = 10; divisors of 10: 1, 2, 5, 10; both concatenation of divisors 12510 and reverse concatenation of divisors 10521 are nonprime numbers.

Crossrefs

Sequence in context: A176114 A057915 A154329 * A253061 A320730 A087943

Adjacent sequences: A176587 A176588 A176589 * A176591 A176592 A176593

Keyword

nonn,base

Author

Jaroslav Krizek, Apr 21 2010

Extensions

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

Status

approved