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A176554 Numbers n such that concatenations of divisors of n are nonprime. 4
1, 2, 4, 5, 6, 8, 10, 11, 12, 14, 15, 16, 17, 18, 19, 20, 22, 23, 24, 25, 26, 27, 28, 29, 30, 32, 33, 34, 35, 36, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

See A037278(n) = concatenation of divisors of n. See A176556 for corresponding values of concatenations. Complement of A176553(n) for n >= 2.

LINKS

Table of n, a(n) for n=1..71.

EXAMPLE

a(6) = 8: divisors of 8 are 1,2,4,8 and their concatenation 1248 is nonprime.

CROSSREFS

Sequence in context: A035500 A080653 A115836 * A284895 A285354 A050505

Adjacent sequences:  A176551 A176552 A176553 * A176555 A176556 A176557

KEYWORD

nonn,base

AUTHOR

Jaroslav Krizek, Apr 20 2010

EXTENSIONS

Edited and extended by Charles R Greathouse IV, Apr 30 2010

STATUS

approved

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Last modified November 15 11:18 EST 2019. Contains 329144 sequences. (Running on oeis4.)