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A181800
Powerful numbers that are the least integer of their prime signature.
16
1, 4, 8, 16, 32, 36, 64, 72, 128, 144, 216, 256, 288, 432, 512, 576, 864, 900, 1024, 1152, 1296, 1728, 1800, 2048, 2304, 2592, 3456, 3600, 4096, 4608, 5184, 5400, 6912, 7200, 7776, 8192, 9216, 10368, 10800, 13824, 14400, 15552, 16384, 18432, 20736, 21600, 27000
OFFSET
1,2
COMMENTS
Apart from 1, all terms in this sequence are multiples of 4. - Charles R Greathouse IV, Dec 13 2016
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..1000 from Charles R Greathouse IV)
FORMULA
Intersection of A001694 and A025487.
PROG
(PARI) is(n)=if(n<4, return(n==1)); my(f=factor(n)); vecmin(f[, 2])>1 && f[, 1]~ == primes(#f~) && f[, 2] == vecsort(f[, 2], , 4) \\ Charles R Greathouse IV, Sep 14 2015
CROSSREFS
Cf. A001694 (powerful numbers), A025487 (least integer of each prime signature).
Sequence in context: A141031 A061011 A359777 * A319180 A075090 A354955
KEYWORD
nonn
AUTHOR
Matthew Vandermast, Dec 02 2010
STATUS
approved