

A167186


Record gaps between nonprime prime powers.


3



3, 4, 7, 9, 17, 40, 41, 74, 151, 307, 312, 408, 424, 912, 1032, 1217, 1872, 2518, 3713, 4920, 5208, 8400, 8520, 8892, 9297, 12840, 16008, 21840, 24360, 35880, 38808, 80760, 102168, 129480, 167160, 183960, 201072, 258720, 290760, 301242, 358848, 375468, 415920
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OFFSET

1,1


LINKS

Donovan Johnson, Table of n, a(n) for n = 1..200


EXAMPLE

17 is in the sequence since A025475(9)  A025475(8) = 49  32 = 17, and no previous gap is larger.
A025475(10)  A025475(9) = 64  49 = 15, but the previous gap is larger, so 15 is not in the sequence.


PROG

(PARI) isA025475(n) = (omega(n) == 1 & !isprime(n))  (n == 1)
d_max=0; n_prev=1; for(n=2, 32e6, if(isA025475(n), d=nn_prev; n_prev=n; if(d>d_max, print(d); d_max=d)))


CROSSREFS

List of nonprime prime powers: A025475.
Gaps between nonprime prime powers: A053707.
Record gaps between prime powers including primes: A121492.
Sequence in context: A108796 A048849 A076211 * A221212 A218278 A101062
Adjacent sequences: A167183 A167184 A167185 * A167187 A167188 A167189


KEYWORD

nonn


AUTHOR

Michael B. Porter, Oct 29 2009, Oct 31 2009, Nov 03 2009


STATUS

approved



