login
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
OFFSET
1,1
LINKS
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.
MATHEMATICA
Join[{3}, DeleteDuplicates[Differences[Select[Range[10^6], PrimePowerQ[#] && !PrimeQ[ #]&]], GreaterEqual]] (* Harvey P. Dale, Feb 28 2023 *)
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=n-n_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: A364684 A048849 A076211 * A221212 A218278 A101062
KEYWORD
nonn
AUTHOR
Michael B. Porter, Oct 29 2009, Oct 31 2009, Nov 03 2009
STATUS
approved